#include<bits/stdc++.h>

#define cp const point &
#define cl const line &
#define cc const circle &
#define LD long double
std::mt19937 rnd(time(0));
const LD eps = 1e-8;
const LD pi = std::numbers::pi;
const LD INF = 1e9;

int sgn(LD x)
{
    return x > eps ? 1 : (x < -eps ? -1 : 0);
}

LD sqr(LD x)
{ return x * x; }

struct point
{
    LD x, y;

    point operator+(cp a) const
    { return {x + a.x, y + a.y}; }

    point operator-(cp a) const
    { return {x - a.x, y - a.y}; }

    point operator*(LD t) const
    { return {x * t, y * t}; }

    point operator/(LD t) const
    { return {x / t, y / t}; }

    point rot(LD t) const
    { return {x * cos(t) - y * sin(t), x * sin(t) + y * cos(t)}; }

    point rot90() const
    { return {-y, x}; }

    LD len2() const
    { return x * x + y * y; }

    LD len() const
    { return sqrtl(x * x + y * y); }

    point unit() const
    {
        double d = len();
        return {x / d, y / d};
    }

    friend bool operator<(cp a, cp b)
    {
        return a.x == b.x ? a.y < b.y : a.x < b.x;
    }

    friend bool operator>(cp a, cp b)
    {
        return a.x == b.x ? a.y > b.y : a.x > b.x;
    }
};

LD dot(cp a, cp b);

bool operator==(cp a, cp b)
{
    return !sgn(dot(a - b, a - b));
}

LD dis(cp a, cp b)//两点距离
{
    return sqrtl(sqr(a.x - b.x) + sqr(a.y - b.y));
}

LD dot(cp a, cp b)//点乘
{
    return a.x * b.x + a.y * b.y;
}

LD det(cp a, cp b)//叉乘
{
    return a.x * b.y - b.x * a.y;
}

bool turn_left(cp a, cp b, cp c)//判断ba是否逆时针转少于180°到ca
{
    return sgn(det(b - a, c - a)) > 0;//大于是严格凸包
}

struct line
{
    point s, t;

    line(point a, point b) : s(a), t(b)
    {}
};

struct circle
{
    point c;
    LD r;

    circle()
    {}

    circle(point C, LD R)
    { c = C, r = R; }
};

bool in_circle(cp a, cc b)
{
    return sgn((b.c - a).len() - b.r) <= 0;
}

circle make_circle(point u, point v)
{
    point p = (u + v) / 2;
    return circle(p, (u - p).len());
}

circle make_circle(cp a, cp b, cp c)
{
    point p = b - a, q = c - a;
    point s(dot(p, p) / 2, dot(q, q) / 2);
    LD d = det(p, q);
    p = point(det(s, point(p.y, q.y)), det(point(p.x, q.x), s)) / d;
    return circle(a + p, p.len());
}

circle min_circle(std::vector<point> p)
{
    circle ret(p[0], 0);
    std::shuffle(p.begin(), p.end(), rnd);
    int len = p.size();
    for (int i = 0; i < len; i++)
        if (!in_circle(p[i], ret))
        {
            ret = circle(p[i], 0);
            for (int j = 0; j < i; j++)
                if (!in_circle(p[j], ret))
                {
                    ret = make_circle(p[j], p[i]);
                    for (int k = 0; k < j; ++k)
                        if (!in_circle(p[k], ret))
                            ret = make_circle(p[i], p[j], p[k]);
                }
        }
    return ret;
}


bool same_dir(cl a, cl b)//判断方向是否一致
{
    return sgn(det(b.t - b.s, a.t - a.s)) == 0 && sgn(dot(b.t - b.s, a.t - a.s)) > 0;
}

bool point_on_line(cp a, cl l)//判断点是否在直线上
{
    return sgn(det(a-l.s, l.t - l.s)) == 0;
}

bool point_on_segment(cp a, cl l)//判断点是否在线段上
{
    return point_on_line(a, l) && sgn(dot(l.s - a, l.t-a )) <= 0;
}

bool two_side(cp a, cp b, cl c)//判断两个点是否在线段的两边
{
    return sgn(det(a - c.s, c.t - c.s)) * sgn(det(b - c.s, c.t - c.s)) < 0;
}

bool intersect_judge(cl a, cl b)
{//判断两个线段是否相交
    if (point_on_segment(a.s, b) || point_on_segment(a.t, b) || point_on_segment(b.s, a) ||
        point_on_segment(b.t, a))
        return true;
    return two_side(a.s, a.t, b) && two_side(b.s, b.t, a);
}

point line_intersect(cl a, cl b)
{//得到两线段的交点
    double s1 = det(a.t - a.s, b.s - a.s);
    double s2 = det(a.t - a.s, b.t - a.s);
    return (b.s * s2 - b.t * s1) / (s2 - s1);
}

bool point_on_ray(cp a, cl b)
{//判断点是否在射线上
    return sgn(det(a - b.s, b.t - b.s)) == 0 && sgn(dot(a - b.s, b.t - b.s)) >= 0;
}

bool ray_intersect_judge(line a, line b)//判断两射线是否相交
{
    double s1, s2;
    s1 = det(a.t - a.s, b.s - a.s);
    s2 = det(a.t - a.s, b.t - a.s);
    if (sgn(s1) == 0 && sgn(s2) == 0)
        return sgn(dot(a.t - a.s, b.s - a.s)) >= 0 || sgn(dot(b.t - b.s, a.s - b.s));
    if (!sgn(s1 - s2) || sgn(s1) == sgn(s2 - s1))return 0;
    std::swap(a, b);
    s1 = det(a.t - a.s, b.s - a.s);
    s2 = det(a.t - a.s, b.t - a.s);
    return sgn(s1) != sgn(s2 - s1);
}

LD point_to_line(cp a, cl b)
{//点到直线的距离
    return abs(det(b.t - b.s, a - b.s)) / dis(b.s, b.t);
}

point project_to_line(cp a, cl b)
{//得到点在线上的投影
    return b.s + (b.t - b.s) * (dot(a - b.s, b.t - b.s) / (b.t - b.s).len2());
}

LD point_to_segment(cp a, cl b)
{//点到线段的距离
    if (b.s == b.t)
        return dis(a, b.s);
    if (sgn(dot(b.s - a, b.t - b.s)) * sgn(dot(b.t - a, b.t - b.s)) <= 0)
        return abs(det(b.t - b.s, a - b.s)) / dis(b.s, b.t);
    return std::min(dis(a, b.s), dis(a, b.t));
}

std::vector<point> convex_hull(std::vector<point> a)
{//凸包，字典序
    int n = (int) a.size(), cnt = 0;
    if (n < 2) return a;
    std::sort(a.begin(), a.end()); // less<pair>
    std::vector<point> ret;
    for (int i = 0; i < n; ++i)
    {
        while (cnt > 1
               && !turn_left(ret[cnt - 1], a[i], ret[cnt - 2]))
            --cnt, ret.pop_back();
        ++cnt, ret.push_back(a[i]);
    }
    int fixed = cnt;
    for (int i = n - 2; i >= 0; --i)
    {
        while (cnt > fixed
               && !turn_left(ret[cnt - 1], a[i], ret[cnt - 2]))
            --cnt, ret.pop_back();
        ++cnt, ret.push_back(a[i]);
    }
    ret.pop_back();
    return ret;
}

std::vector<point> minkovski(std::vector<std::vector<point>> a)
{
    if (a[0].size() == 1)
        return a[1];
    if (a[1].size() == 1)
        return a[0];
    for (int i = 0; i < 2; i++)a[i].push_back(a[i].front());
    int i[2] = {0, 0}, len[2] = {(int) a[0].size() - 1, (int) a[1].size() - 1};
    std::vector<point> ret;
    ret.push_back(a[0][0] + a[1][0]);
    do
    {
        int d = sgn(det(a[1][i[1] + 1] - a[1][i[1]], a[0][i[0] + 1] - a[0][i[0]])) >= 0;
        ret.push_back(a[d][i[d] + 1] - a[d][i[d]] + ret.back());
        i[d] = (i[d] + 1) % len[d];
    }
    while (i[0] || i[1]);
    return ret;
}

struct Convex
{
    int n;
    std::vector<point> a, upper, lower;

    Convex(std::vector<point> _a) : a(_a)
    {
        n = a.size();
        int k = 0;
        for (int i = 1; i < n; i++)if (a[k] < a[i])k = i;
        for (int i = 0; i <= k; i++) lower.push_back(a[i]);
        for (int i = k; i < n; i++) upper.push_back(a[i]);
        upper.push_back(a[0]);
    }

    std::pair<LD, int> get_tan(std::vector<point> &con, point vec)
    {
        int l = 0, r = (int) con.size() - 2;
        for (; l + 1 < r;)
        {
            int mid = (l + r) / 2;
            if (sgn(det(con[mid + 1] - con[mid], vec)) > 0)r = mid;
            else l = mid;
        }
        return std::max(std::make_pair(det(vec, con[r]), r), std::make_pair(det(vec, con[0]), 0));
    }

    void upd_tan(cp p, int id, int &i0, int &i1)
    {
        if (sgn(det(a[i0] - p, a[id] - p)) > 0) i0 = id;
        if (sgn(det(a[i1] - p, a[id] - p)) < 0) i1 = id;
    }

    void search(int l, int r, point p, int &i0, int &i1)
    {
        if (l == r)return;
        upd_tan(p, l % n, i0, i1);
        int sl = sgn(det(a[l % n] - p, a[(l + 1) % n] - p));
        for (; l + 1 < r;)
        {
            int mid = (l + r) / 2;
            int smid = sgn(det(a[mid % n] - p, a[(mid + 1) % n] - p));
            if (smid == sl)l = mid;
            else r = mid;
        }
        upd_tan(p, r % n, i0, i1);
    }

    int search(point u, point v, int l, int r)
    {
        int sl = sgn(det(v - u, a[l % n] - u));
        for (; l + 1 < r;)
        {
            int mid = (l + r) / 2;
            int smid = sgn(det(v - u, a[mid % n] - u));
            if (smid == sl) l = mid;
            else r = mid;
        }
        return l % n;
    }

    //判定点是否在凸包内，在边界返回true
    bool contain(point p)
    {
        if (p.x < lower[0].x || p.x > lower.back().x)return false;
        int id = std::lower_bound(lower.begin(), lower.end(), point(p.x, -INF)) - lower.begin();
        if (lower[id].x == p.x)
        {
            if (lower[id].y > p.y)return false;
        }
        else if (det(lower[id - 1] - p, lower[id] - p) < 0)
            return false;
        id = std::lower_bound(upper.begin(), upper.end(), point(p.x, INF), std::greater<point>()) - upper.begin();
        if (upper[id].x == p.x)
        {
            if (upper[id].y < p.y)return false;
        }
        else if (det(upper[id - 1] - p, upper[id] - p) < 0)
            return false;
        return true;
    }
};

std::vector<point> Minkovski(std::vector<std::vector<point>> a)
{                                                            //闵可夫斯基和
    std::vector<point> S;
    int n = a[0].size(), m = a[1].size();
    std::vector<point> A(n ), B(m );
    for (int i = 0; i < n - 1; i++) A[i] = a[0][i + 1] - a[0][i];
    A[n - 1] = a[0][0] - a[0][n - 1];
    for (int i = 0; i < m - 1; i++) B[i] = a[1][i + 1] - a[1][i];
    B[m - 1] = a[1][0] - a[1][m - 1];                                                             //将两个凸包上的边向量都存入a,b中
    S.push_back(a[0][0] + a[1][0]);
    int p1 = 0, p2 = 0;
    while (p1 < n && p2 < m)
    {
        LD d = det(A[p1], B[p2]);
        if (d > 0)
            S.push_back(S.back()+A[p1++]);
        else if (d < 0)
            S.push_back(S.back()+B[p2++]);
        else
        {
            if(dot(A[p1],B[p1])>=0)
                S.push_back(S.back()+A[p1++]);
            else
            {
                auto [x,y]=A[p1];
                if(x>0)
                    S.push_back(S.back()+A[p1++]);
                else if(x<0)
                    S.push_back(S.back()+B[p2++]);
                else
                {
                    if(y>0)
                        S.push_back(S.back()+A[p1++]);
                    else S.push_back(S.back()+B[p2++]);
                }
            }
        }
    }
    while (p1 < n)
        S.push_back(S.back() + A[p1++]);
    while (p2 < m)
        S.push_back(S.back() + B[p2++]);
    return S;
}

void print(std::vector<point> res)
{
    std::cout << "print:\n";
    int cnt=0;
    for (auto [x, y]: res)
        std::cout <<++cnt<<' '<< x << ' ' << y << std::endl;
    std::cout << "end\n";
}

void solve()
{
    int  n;
    std::cin>>n;
    std::vector<point>pu(n);
    for(int i=0;i<n;i++)
        std::cin>>pu[i].x>>pu[i].y;
    int cnt=0;
    std::sort(pu.begin(), pu.end()); // less<pair>
//    print(pu);
    std::vector<int>vis(n);
    std::vector<std::pair<point,int>>ppu(n);
    for(int i=0;i<n;i++)
        ppu[i]=std::make_pair(pu[i],i);
    auto ret= convex_hull(pu) ;
    std::map<std::pair<LD,LD>,int>mp;
    for(auto [x,y]:ret)
        mp[{x,y}]=1;
    for(int i=0;i<n;i++)
    {
        auto [x,y]=pu[i];
        vis[i]=mp[{x,y}];
    }
    int ans=1;
    for(int i=0;i<n;i++)
    {
        if(vis[i]) continue;
        point base=pu[i];
        std::sort(ppu.begin(),ppu.end(),[&](std::pair<point,int> x,std::pair<point,int> y){
            auto u=x.first-base,v=y.first-base;
            if(u.x==0&&u.y==0)
                return true;
            if(v.x==0&&v.y==0)
                return false;
            if(u.x*v.x<0)
                return u.x>0;
            else if(u.x*v.x>0)
                return u.y*v.x<v.y*u.x;
            else
            {
                if(u.x==0)
                {
                    if(u.y<0)
                        return false;
                    else return v.x<0;
                }
                else
                {
                    if(v.y<0)
                        return true;
                    else return u.x>0;
                }
            }
        });
//        if(i==3)
//            std::cout<<"HERE"<<std::endl;
        for(int j=1;j<n;j++)
        {
//            std::cout<<ppu[j].second<<' ';
            if((vis[ppu[j].second])&&vis[ppu[j+1==n?1:j+1].second])
              ans++;
        }
//        std::cout<<std::endl;
//        std::cout<<i<<' '<<ans<<std::endl;
    }
    std::cout<<ans<<std::endl;
}

int main()
{
    std::ios::sync_with_stdio(false);
    std::cin.tie(0), std::cout.tie(0);
    std::cout << std::fixed << std::setprecision(10);
    int T = 1;
//    std::cin>>T;
    while (T--)
        solve();
}