#include <bits/stdc++.h>
using namespace std;
#define ll __int128
#define pb push_back
#define ldb double


//-----------------Big int-----------------------//


// Fast Fourier transform
// https://cp-algorithms.com/algebra/fft.html
// https://drive.google.com/file/d/1B9BIfATnI_qL6rYiE5hY9bh20SMVmHZ7/view

using cpx = complex<double>;
const double PI = acos(-1);
vector<cpx> roots = {{0, 0}, {1, 0}};

void ensure_capacity(int min_capacity) {
    for (int len = roots.size(); len < min_capacity; len *= 2) {
        for (int i = len >> 1; i < len; i++) {
            roots.emplace_back(roots[i]);
            double angle = 2 * PI * (2 * i + 1 - len) / (len * 2);
            roots.emplace_back(cos(angle), sin(angle));
        }
    }
}

void fft(vector<cpx> &z, bool inverse) {
    int n = z.size();
    assert((n & (n - 1)) == 0);
    ensure_capacity(n);
    for (unsigned i = 1, j = 0; i < n; i++) {
        int bit = n >> 1;
        for (; j >= bit; bit >>= 1)
            j -= bit;
        j += bit;
        if (i < j)
            swap(z[i], z[j]);
    }
    for (int len = 1; len < n; len <<= 1) {
        for (int i = 0; i < n; i += len * 2) {
            for (int j = 0; j < len; j++) {
                cpx root = inverse ? conj(roots[j + len]) : roots[j + len];
                cpx u = z[i + j];
                cpx v = z[i + j + len] * root;
                z[i + j] = u + v;
                z[i + j + len] = u - v;
            }
        }
    }
    if (inverse)
        for (int i = 0; i < n; i++)
            z[i] /= n;
}

vector<int> multiply_bigint(const vector<int> &a, const vector<int> &b, int base) {
    int need = a.size() + b.size();
    int n = 1;
    while (n < need)
        n <<= 1;
    vector<cpx> p(n);
    for (size_t i = 0; i < n; i++) {
        p[i] = cpx(i < a.size() ? a[i] : 0, i < b.size() ? b[i] : 0);
    }
    fft(p, false);
    // a[w[k]] = (p[w[k]] + conj(p[w[n-k]])) / 2
    // b[w[k]] = (p[w[k]] - conj(p[w[n-k]])) / (2*i)
    vector<cpx> ab(n);
    cpx r(0, -0.25);
    for (int i = 0; i < n; i++) {
        int j = (n - i) & (n - 1);
        ab[i] = (p[i] * p[i] - conj(p[j] * p[j])) * r;
    }
    fft(ab, true);
    vector<int> result(need);
    long long carry = 0;
    for (int i = 0; i < need; i++) {
        long long d = (long long)(ab[i].real() + 0.5) + carry;
        carry = d / base;
        result[i] = d % base;
    }
    return result;
}

vector<int> multiply_mod(const vector<int> &a, const vector<int> &b, int m) {
    int need = a.size() + b.size() - 1;
    int n = 1;
    while (n < need)
        n <<= 1;
    vector<cpx> A(n);
    for (size_t i = 0; i < a.size(); i++) {
        int x = (a[i] % m + m) % m;
        A[i] = cpx(x & ((1 << 15) - 1), x >> 15);
    }
    fft(A, false);

    vector<cpx> B(n);
    for (size_t i = 0; i < b.size(); i++) {
        int x = (b[i] % m + m) % m;
        B[i] = cpx(x & ((1 << 15) - 1), x >> 15);
    }
    fft(B, false);

    vector<cpx> fa(n);
    vector<cpx> fb(n);
    for (int i = 0, j = 0; i < n; i++, j = n - i) {
        cpx a1 = (A[i] + conj(A[j])) * cpx(0.5, 0);
        cpx a2 = (A[i] - conj(A[j])) * cpx(0, -0.5);
        cpx b1 = (B[i] + conj(B[j])) * cpx(0.5, 0);
        cpx b2 = (B[i] - conj(B[j])) * cpx(0, -0.5);
        fa[i] = a1 * b1 + a2 * b2 * cpx(0, 1);
        fb[i] = a1 * b2 + a2 * b1;
    }

    fft(fa, true);
    fft(fb, true);
    vector<int> res(need);
    for (int i = 0; i < need; i++) {
        long long aa = (long long)(fa[i].real() + 0.5);
        long long bb = (long long)(fb[i].real() + 0.5);
        long long cc = (long long)(fa[i].imag() + 0.5);
        res[i] = (aa % m + (bb % m << 15) + (cc % m << 30)) % m;
    }
    return res;
}


constexpr int digits(int base) noexcept {
    return base <= 1 ? 0 : 1 + digits(base / 10);
}

constexpr int base = 1000'000'000;
constexpr int base_digits = digits(base);

constexpr int fft_base = 10'000;  // fft_base^2 * n / fft_base_digits <= 10^15 for double
constexpr int fft_base_digits = digits(fft_base);

struct bigint {
    // value == 0 is represented by empty z
    vector<int> z;  // digits

    // sign == 1 <==> value >= 0
    // sign == -1 <==> value < 0
    int sign;

    bigint(long long v = 0) { *this = v; }

    bigint &operator=(long long v) {
        sign = v < 0 ? -1 : 1;
        v *= sign;
        z.clear();
        for (; v > 0; v = v / base)
            z.push_back((int)(v % base));
        return *this;
    }

    bigint(const string &s) { read(s); }

    bigint &operator+=(const bigint &other) {
        if (sign == other.sign) {
            for (int i = 0, carry = 0; i < other.z.size() || carry; ++i) {
                if (i == z.size())
                    z.push_back(0);
                z[i] += carry + (i < other.z.size() ? other.z[i] : 0);
                carry = z[i] >= base;
                if (carry)
                    z[i] -= base;
            }
        } else if (other != 0 /* prevent infinite loop */) {
            *this -= -other;
        }
        return *this;
    }

    friend bigint operator+(bigint a, const bigint &b) {
        a += b;
        return a;
    }

    bigint &operator-=(const bigint &other) {
        if (sign == other.sign) {
            if ((sign == 1 && *this >= other) || (sign == -1 && *this <= other)) {
                for (int i = 0, carry = 0; i < other.z.size() || carry; ++i) {
                    z[i] -= carry + (i < other.z.size() ? other.z[i] : 0);
                    carry = z[i] < 0;
                    if (carry)
                        z[i] += base;
                }
                trim();
            } else {
                *this = other - *this;
                this->sign = -this->sign;
            }
        } else {
            *this += -other;
        }
        return *this;
    }

    friend bigint operator-(bigint a, const bigint &b) {
        a -= b;
        return a;
    }

    bigint &operator*=(int v) {
        if (v < 0)
            sign = -sign, v = -v;
        for (int i = 0, carry = 0; i < z.size() || carry; ++i) {
            if (i == z.size())
                z.push_back(0);
            long long cur = (long long)z[i] * v + carry;
            carry = (int)(cur / base);
            z[i] = (int)(cur % base);
        }
        trim();
        return *this;
    }

    bigint operator*(int v) const { return bigint(*this) *= v; }

    friend pair<bigint, bigint> divmod(const bigint &a1, const bigint &b1) {
        int norm = base / (b1.z.back() + 1);
        bigint a = a1.abs() * norm;
        bigint b = b1.abs() * norm;
        bigint q, r;
        q.z.resize(a.z.size());

        for (int i = (int)a.z.size() - 1; i >= 0; i--) {
            r *= base;
            r += a.z[i];
            int s1 = b.z.size() < r.z.size() ? r.z[b.z.size()] : 0;
            int s2 = b.z.size() - 1 < r.z.size() ? r.z[b.z.size() - 1] : 0;
            int d = (int)(((long long)s1 * base + s2) / b.z.back());
            r -= b * d;
            while (r < 0)
                r += b, --d;
            q.z[i] = d;
        }

        q.sign = a1.sign * b1.sign;
        r.sign = a1.sign;
        q.trim();
        r.trim();
        return {q, r / norm};
    }

    friend bigint sqrt(const bigint &a1) {
        bigint a = a1;
        while (a.z.empty() || a.z.size() % 2 == 1)
            a.z.push_back(0);

        int n = a.z.size();

        int firstDigit = (int)::sqrt((double)a.z[n - 1] * base + a.z[n - 2]);
        int norm = base / (firstDigit + 1);
        a *= norm;
        a *= norm;
        while (a.z.empty() || a.z.size() % 2 == 1)
            a.z.push_back(0);

        bigint r = (long long)a.z[n - 1] * base + a.z[n - 2];
        firstDigit = (int)::sqrt((double)a.z[n - 1] * base + a.z[n - 2]);
        int q = firstDigit;
        bigint res;

        for (int j = n / 2 - 1; j >= 0; j--) {
            for (;; --q) {
                bigint r1 = (r - (res * 2 * base + q) * q) * base * base +
                            (j > 0 ? (long long)a.z[2 * j - 1] * base + a.z[2 * j - 2] : 0);
                if (r1 >= 0) {
                    r = r1;
                    break;
                }
            }
            res *= base;
            res += q;

            if (j > 0) {
                int d1 = res.z.size() + 2 < r.z.size() ? r.z[res.z.size() + 2] : 0;
                int d2 = res.z.size() + 1 < r.z.size() ? r.z[res.z.size() + 1] : 0;
                int d3 = res.z.size() < r.z.size() ? r.z[res.z.size()] : 0;
                q = (int)(((long long)d1 * base * base + (long long)d2 * base + d3) / (firstDigit * 2));
            }
        }

        res.trim();
        return res / norm;
    }

    bigint operator/(const bigint &v) const { return divmod(*this, v).first; }

    bigint operator%(const bigint &v) const { return divmod(*this, v).second; }

    bigint &operator/=(int v) {
        if (v < 0)
            sign = -sign, v = -v;
        for (int i = (int)z.size() - 1, rem = 0; i >= 0; --i) {
            long long cur = z[i] + rem * (long long)base;
            z[i] = (int)(cur / v);
            rem = (int)(cur % v);
        }
        trim();
        return *this;
    }

    bigint operator/(int v) const { return bigint(*this) /= v; }

    int operator%(int v) const {
        if (v < 0)
            v = -v;
        int m = 0;
        for (int i = (int)z.size() - 1; i >= 0; --i)
            m = (int)((z[i] + m * (long long)base) % v);
        return m * sign;
    }

    bigint &operator*=(const bigint &v) {
        *this = *this * v;
        return *this;
    }

    bigint &operator/=(const bigint &v) {
        *this = *this / v;
        return *this;
    }

    bigint &operator%=(const bigint &v) {
        *this = *this % v;
        return *this;
    }

    bool operator<(const bigint &v) const {
        if (sign != v.sign)
            return sign < v.sign;
        if (z.size() != v.z.size())
            return z.size() * sign < v.z.size() * v.sign;
        for (int i = (int)z.size() - 1; i >= 0; i--)
            if (z[i] != v.z[i])
                return z[i] * sign < v.z[i] * sign;
        return false;
    }

    bool operator>(const bigint &v) const { return v < *this; }

    bool operator<=(const bigint &v) const { return !(v < *this); }

    bool operator>=(const bigint &v) const { return !(*this < v); }

    bool operator==(const bigint &v) const { return sign == v.sign && z == v.z; }

    bool operator!=(const bigint &v) const { return !(*this == v); }

    void trim() {
        while (!z.empty() && z.back() == 0)
            z.pop_back();
        if (z.empty())
            sign = 1;
    }

    bool isZero() const { return z.empty(); }

    friend bigint operator-(bigint v) {
        if (!v.z.empty())
            v.sign = -v.sign;
        return v;
    }

    bigint abs() const { return sign == 1 ? *this : -*this; }

    long long longValue() const {
        long long res = 0;
        for (int i = (int)z.size() - 1; i >= 0; i--)
            res = res * base + z[i];
        return res * sign;
    }

    ldb ldbValue() const {
        ldb res = 0;
        for (int i = (int)z.size() - 1; i >= 0; i--)
            res = res * base + z[i];
        return res * sign;
    }

    friend bigint gcd(const bigint &a, const bigint &b) { return b.isZero() ? a : gcd(b, a % b); }

    friend bigint lcm(const bigint &a, const bigint &b) { return a / gcd(a, b) * b; }

    void read(const string &s) {
        sign = 1;
        z.clear();
        int pos = 0;
        while (pos < s.size() && (s[pos] == '-' || s[pos] == '+')) {
            if (s[pos] == '-')
                sign = -sign;
            ++pos;
        }
        for (int i = (int)s.size() - 1; i >= pos; i -= base_digits) {
            int x = 0;
            for (int j = max(pos, i - base_digits + 1); j <= i; j++)
                x = x * 10 + s[j] - '0';
            z.push_back(x);
        }
        trim();
    }

    friend istream &operator>>(istream &stream, bigint &v) {
        string s;
        stream >> s;
        v.read(s);
        return stream;
    }

    friend ostream &operator<<(ostream &stream, const bigint &v) {
        if (v.sign == -1)
            stream << '-';
        stream << (v.z.empty() ? 0 : v.z.back());
        for (int i = (int)v.z.size() - 2; i >= 0; --i)
            stream << setw(base_digits) << setfill('0') << v.z[i];
        return stream;
    }

    static vector<int> convert_base(const vector<int> &a, int old_digits, int new_digits) {
        vector<long long> p(max(old_digits, new_digits) + 1);
        p[0] = 1;
        for (int i = 1; i < p.size(); i++)
            p[i] = p[i - 1] * 10;
        vector<int> res;
        long long cur = 0;
        int cur_digits = 0;
        for (int v : a) {
            cur += v * p[cur_digits];
            cur_digits += old_digits;
            while (cur_digits >= new_digits) {
                res.push_back(int(cur % p[new_digits]));
                cur /= p[new_digits];
                cur_digits -= new_digits;
            }
        }
        res.push_back((int)cur);
        while (!res.empty() && res.back() == 0)
            res.pop_back();
        return res;
    }

    bigint operator*(const bigint &v) const {
        if (min(z.size(), v.z.size()) < 150)
            return mul_simple(v);
        bigint res;
        res.sign = sign * v.sign;
        res.z = multiply_bigint(convert_base(z, base_digits, fft_base_digits),
                                convert_base(v.z, base_digits, fft_base_digits), fft_base);
        res.z = convert_base(res.z, fft_base_digits, base_digits);
        res.trim();
        return res;
    }

    bigint mul_simple(const bigint &v) const {
        bigint res;
        res.sign = sign * v.sign;
        res.z.resize(z.size() + v.z.size());
        for (int i = 0; i < z.size(); ++i)
            if (z[i])
                for (int j = 0, carry = 0; j < v.z.size() || carry; ++j) {
                    long long cur = res.z[i + j] + (long long)z[i] * (j < v.z.size() ? v.z[j] : 0) + carry;
                    carry = (int)(cur / base);
                    res.z[i + j] = (int)(cur % base);
                }
        res.trim();
        return res;
    }
};



//-----------------Big int-----------------------//

#define ll bigint


/*ll gcd(ll a,ll b){
	return a==0?b:gcd(b%a,a);
}*/
ll myabs(ll a){return a<0?-a:a;}

struct frac{
	ll p,q;

	frac():p(0),q(1){}
	frac(ll x):p(x),q(1){}
	frac(ll a,ll b){
		if(b<0)b=-b,a=-a;
		ll g=gcd(myabs(a),b);
		p=a/g;
		q=b/g;
	}
	ldb to_ldb(){
		return p.ldbValue()/q.ldbValue();
	}
	void Print(){
		printf("%lf",to_ldb());
	}
};
frac operator + (frac a,frac b){
	return frac(a.p*b.q+b.p*a.q,a.q*b.q);
}
frac operator - (frac a,frac b){
	return frac(a.p*b.q-b.p*a.q,a.q*b.q);
}
frac operator - (frac a){
	return frac(-a.p,a.q);
}
frac operator * (frac a,frac b){
	return frac(a.p*b.p,a.q*b.q);
}
frac operator * (frac a,ll b){
	return frac(a.p*b,a.q);
}
frac operator / (frac a,frac b){
	return frac(a.p*b.q,a.q*b.p);
}
frac operator / (frac a,ll b){
	return frac(a.p,a.q*b);
}
bool operator < (frac a,frac b){
	return a.p*b.q < b.p*a.q;
}
bool operator < (frac a,ll b){
	return a.p < b*a.q;
}
bool operator == (frac a,frac b){
	return a.p*b.q == b.p*a.q;
}
bool operator == (frac a,ll b){
	return a.p == b*a.q;
}
bool operator <= (frac a,frac b){
	return a<b || a==b;
}
bool operator <= (frac a,ll b){
	return a<b || a==b;
}

int sgn(frac x){
	if(x<0)return -1;
	if(x==0)return 0;
	return 1;
}

struct pt{
	frac x,y;

	pt():x(0),y(0){}
	pt(ll a,ll b):x(a),y(b){}
	pt(frac a,frac b):x(a),y(b){}

	void Print(){
		printf("(");
		x.Print();
		printf(", ");
		y.Print();
		printf(") ");
	}
};
pt operator + (pt a,pt b){return pt(a.x+b.x,a.y+b.y);}
pt operator - (pt a,pt b){return pt(a.x-b.x,a.y-b.y);}
pt operator - (pt a){return pt(-a.x,-a.y);}
pt operator * (pt a,ll b){return pt(a.x*b,a.y*b);}
pt operator / (pt a,ll b){return pt(a.x/b,a.y/b);}
pt operator * (pt a,frac b){return pt(a.x*b,a.y*b);}
pt operator / (pt a,frac b){return pt(a.x/b,a.y/b);}

frac cross(pt a,pt b){return a.x*b.y-a.y*b.x;}
frac dot(pt a,pt b){return a.x*b.x+a.y*b.y;}

ldb dist(pt a,pt b){
	ldb x1=a.x.to_ldb();
	ldb y1=a.y.to_ldb();
	ldb x2=b.x.to_ldb();
	ldb y2=b.y.to_ldb();
	ldb dx=x1-x2;
	ldb dy=y1-y2;
	return sqrt(dx*dx+dy*dy);
}

pt perp(pt a){return pt(-a.y,a.x);}

struct line{
	pt from,to;
	pt v;
	frac c;

	line(pt a,pt b){
		from=a;
		to=b;
		v=b-a;
		c=cross(v,a);
	}

	line(pt a,pt b,pt dir){
		from=a;
		to=b;
		v=dir;
		c=cross(v,a);
	}

	frac side(pt p){
		return -cross(v,p)+c;
	}

	frac offs(pt p){
		return dot(v,p);
	}

	bool onRay(pt p){
		return offs(from)<offs(p);
	}
	bool onSegment(pt p){
		return offs(from)<=offs(p) && offs(p)<=offs(to);
	}
};
pt inter(line a,line b){
	return (b.v*a.c-a.v*b.c)/cross(a.v,b.v);
}
bool parallel(line a,line b){
	return cross(a.v,b.v)==0;
}

vector<pt> poly;
int n;
vector<line> cand;

line GetCand(pt from,pt to){
	line a=line(from,to);
	bool hasL=false,hasR=false;
	pt L,R;
	for(int i=0;i<n;i++){
		int j=(i+1)%n;
		int s1=sgn(a.side(poly[i]));
		int s2=sgn(a.side(poly[j]));
		if(s1!=0 && s2!=0){
			if(s1!=s2){
				pt p=inter(a,line(poly[i],poly[j]));
				if(!(a.side(p)==0)){
					a.from.Print();
					a.to.Print();
					printf(" x ");
					poly[i].Print();
					poly[j].Print();
					printf(" => ");
					p.Print();
					printf("\n");
				}
				assert(a.side(p)==0);
				if(a.onRay(p)){
					if(!hasL || a.offs(p)<a.offs(L)){
						L=p;hasL=true;
					}
					if(!hasR || a.offs(p)<a.offs(R)){
						R=p;hasR=true;
					}
				}
			}
		}else if(s1==0 && s2==0){

		}else{
			pt p;
			if(s1==0){
				p=poly[i];
			}else{
				p=poly[j];
			}
			int s3=s1+s2;
			if(a.onRay(p)){
				if(s3==-1){
					if(!hasL || a.offs(p)<a.offs(L)){
						L=p;hasL=true;
					}
				}else{
					if(!hasR || a.offs(p)<a.offs(R)){
						R=p;hasR=true;
					}
				}
			}
		}
	}

	//printf("GetCand ");
	//from.Print();
	//to.Print();
	//printf("%i %i\n",hasL,hasR);
	//L.Print();
	//R.Print();
	//printf("\n");

	if(!hasL && !hasR)return line(from,from);
	if(!hasL)return line(from,R,to-from);
	if(!hasR)return line(from,L,to-from);

	if(a.offs(L)<a.offs(R)){
		return line(from,R,to-from);
	}else{
		return line(from,L,to-from);
	}
}

bool Inside(pt p){
	int cnt=0;
	for(int i=0;i<n;i++){
		int j=(i+1)%n;
		line seg=line(poly[i],poly[j]);
		if(seg.side(p)==0 && seg.onSegment(p))return true;
		cnt+=((p.y<poly[i].y)-(p.y<poly[j].y))*sgn(cross(poly[i]-p,poly[j]-p))>0;
	}
	return cnt%2==1;
}

pt S,E;

const int N=105;
const ldb inf=1e18;
ldb dp[N];
bool was[N];
vector<pair<int,ldb>> G[N];

int main(){
	scanf("%i",&n);
	for(int i=1;i<=n;i++){
		int x,y;
		scanf("%i %i",&x,&y);
		poly.pb(pt(x,y));
	}
	int sx,sy,ex,ey;
	scanf("%i %i",&sx,&sy);
	S=pt(sx,sy);
	scanf("%i %i",&ex,&ey);
	E=pt(ex,ey);

	for(pt p:poly){
		cand.pb(GetCand(E,p));

		//cand.back().from.Print();
		//cand.back().to.Print();
		//printf("\n");
	}
	cand.pb(GetCand(E,S));

	for(int i=0;i<n;i++){
		for(int j=i+1;j<n;j++){
			line seg=GetCand(poly[i],poly[j]);
			ldb d=dist(poly[i],poly[j]);

			//printf("Ray %i - %i: ",i+1,j+1);
			//seg.to.Print();
			//printf("\n");

			if(seg.onSegment(poly[j]) && Inside((poly[i]+poly[j])/2)){
				G[i].pb({j,d});
				G[j].pb({i,d});
				//printf("Edge\n");
			}
		}
	}
	for(int i=0;i<n;i++){
		line seg=GetCand(S,poly[i]);
		ldb d=dist(S,poly[i]);

		//printf("Ray S - %i: ",i+1);
		//seg.to.Print();
		//printf("\n");

		if(seg.onSegment(poly[i])){
			G[n].pb({i,d});
			//printf("Edge\n");
		}
	}
	for(int i=0;i<n;i++)dp[i]=inf;
	dp[n]=0;
	while(true){
		ldb now=inf;
		int best=-1;
		for(int j=0;j<=n;j++){
			if(!was[j] && dp[j]<now){
				now=dp[j];
				best=j;
			}
		}
		if(best==-1)break;
		was[best]=true;
		for(auto e:G[best]){
			dp[e.first]=min(dp[e.first],dp[best]+e.second);
		}
	}
	ldb ans=inf;
	for(int i=0;i<=n;i++){
		if(was[i]){
			pt p=i==n?S:poly[i];
			//if(i<n)printf("Try %i\n",i+1);
			//else printf("Try S\n");
			for(int j=0;j<cand.size();j++){
				line seg=cand[j];
				if(seg.v.x==0 && seg.v.y==0)continue;

				//printf("Seg %i\n",j);
				//seg.to.Print();
				//printf("\n");

				int s=sgn(seg.side(p));
				//printf("%i\n",s);
				if(s==0){
					if(seg.onSegment(p)){
						ans=min(ans,dp[i]);
						//printf("ANS %.12lf\n",dp[i]);
					}
				}else{
					pt dir=perp(seg.v);
					if(s==-1)dir=-dir;

					//printf("Dir ");
					//seg.v.Print();
					//dir.Print();
					//printf("\n");

					//printf("===================================\n");
					line ray=GetCand(p,p+dir);

					//printf("Perp ray ");
					//ray.from.Print();
					//ray.to.Print();
					//printf("\n");

					if(!parallel(ray,seg)){
						pt o=inter(ray,seg);
						if(seg.onSegment(o) && ray.onSegment(o)){
							ans=min(ans,dp[i]+dist(p,o));
							//printf("ANS %.12lf\n",dp[i]+dist(p,o));
						}
					}

					ray=GetCand(p,seg.to);
					if(ray.onSegment(seg.to) && Inside((p+seg.to)/2)){
						ans=min(ans,dp[i]+dist(p,seg.to));
					}
				}
			}
		}
	}
	printf("%.12lf\n",ans);
	return 0;
}