#include<bits/stdc++.h>
#define F(i, a, b) for(int i = a; i <= b; i ++)
#define Fd(i, a, b) for(int i = a; i >= b; i --)
#define int long long
#define pii pair<int, int>
#define fi first
#define se second
using namespace std;
typedef double db;
const db eps = 1e-10;
int sgn(db x) {
    if(fabs(x) < eps) return 0;
    else return x < 0 ? -1 : 1;
}
struct point {
    db x, y;
    int id;
    point() {}
    point(db x, db y, int id) : x(x), y(y), id(id) {}
    point operator + (point B) {return point(x + B.x, y + B.y, id);}
    point operator - (point B) {return point(x - B.x, y - B.y, id);}
    bool operator == (point B) {return sgn(x - B.x) == 0 && sgn(y - B.y) == 0;}
    bool operator < (point B) {return sgn(x - B.x) < 0 || (sgn(x - B.x) == 0 && sgn(y - B.y) < 0);}
};
// bool cmp(point a, point b) {
//     return sgn(a.y - b.y) == 0 ? sgn(a.x - b.x) < 0 : sgn(a.y - b.y) <= 0; 
// }
db cross(point A, point B) {return A.x * B.y - A.y * B.x;}
bool get_region(point a) {
    return a.y <= 0 && (a.x < 0 || a.y < 0);
}
point o = {0, 0, 0};
bool cmp1(point a, point b) { // 极角排序 逆时针
    point p = a - o, q = b - o;
    if(sgn(atan2(p.y, p.x) - atan2(q.y, q.x)) == 0) return p.x < p.y;
    return atan2(p.y, p.x) < atan2(q.y, q.x);
}
bool cmp2(point a, point b) {
    point p = a - o, q = b - o;
    if(sgn(atan2(p.y, p.x) - atan2(q.y, q.x)) == 0) return p.x > p.y;
    return atan2(p.y, p.x) > atan2(q.y, q.x);
}
// bool cmp1(point a, point b) {
//     point p = a - o, q = b - o;
//     int r1 = get_region(a), r2 = get_region(b);
//     if(r1 != r2) return r1 < r2;
//     if(cross(p, q) == 0) return a.x < b.x;
//     return cross(p, q) > 0;
// }
// bool cmp2(point a, point b) {
//     point p = a - o, q = b - o;
//     int r1 = get_region(a), r2 = get_region(b);
//     if(r1 != r2) return r1 > r2;
//     if(cross(p, q) == 0) return a.x < b.x;
//     return cross(p, q) < 0;
// }
const int N = 2005;

int convex_hull(vector<point> p, int n, int *ch) {
    int v = 0;
    F(i, 0, n - 1) {
        while(v >= 2 && sgn(cross(p[ch[v - 1]] - p[ch[v - 2]], p[i] - p[ch[v - 1]])) <= 0) v --;
        ch[v ++] = i;
    } int j = v;
    Fd(i, n - 2, 0) {
        while(v > j && sgn(cross(p[ch[v - 1]] - p[ch[v - 2]], p[i] - p[ch[v - 1]])) <= 0) v --;
        ch[v ++] = i;
    } 
    return n > 1 ? v - 1 : v;
}

int ch[N], vst[N];

void sol() {
    int n; cin >> n;
    vector<point> a(n);
    F(i, 0, n - 1) {
        int x, y; cin >> x >> y;
        a[i].x = x, a[i].y = y;
    }
    sort(a.begin(), a.end());
    int m = convex_hull(a, n, ch);
    F(i, 0, n - 1) a[i].id = i;
    // cout << m << endl;
    // F(i, 0, m - 1) cout << ch[i] << " \n" [i == m - 1];
    F(i, 0, m - 1) vst[ch[i]] = 1;
    int res = 0;
    F(i, 0, m - 1) {
        int l = ch[i], r = ch[(i + 1) % m];
        // cout << l << " " << r << "\n";
        auto b = a, c = a;
        vector<point> tmp(n);
        o = a[l];
        sort(b.begin(), b.end(), cmp1);
        o = a[r];
        sort(c.begin(), c.end(), cmp2);
        int b0, b1;
        F(j, 0, n - 1) {
            if(b[j].id == a[r].id) {
                b0 = (j + 1) % n;
                break;
            }
        }
        F(j, 0, n - 1) {
            if(c[j].id == a[l].id) {
                b1 = (j + 1) % n;
                break;
            }
        }
        // cout << b0 << " " << b1 << endl;
        // cout << 1 << endl;
        // cout << "szb: " << b.size() << "\n";
        vector<int> pos1(n), pos2(n), ok(n);
        int cnt = 0, tot = 0;
        for(int j = b0; tot < n; j = (j + 1) % n) {
            tot ++;
            tmp[cnt].x = b[j].x, tmp[cnt].y = b[j].y, tmp[cnt ++].id = b[j].id;
        }
        b = tmp;
        // F(j, 0, n - 1) cout << b[j].id << " \n" [j == n - 1];
        // cout << n << endl;
        F(j, 0, n - 1) pos1[b[j].id] = j;
        // cout << 1 << endl;
        cnt = 0, tot = 0;
        for(int j = b1; tot < n; j = (j + 1) % n) {
            tot ++;
            tmp[cnt].x = c[j].x, tmp[cnt].y = c[j].y, tmp[cnt ++].id = c[j].id;
        }
        c = tmp;
        F(j, 0, n - 1) pos2[c[j].id] = j;

        // cout << 1 << endl;
        // F(j, 0, n - 1) cout << b[j].id << " \n" [j == n - 1];
        // F(j, 0, n - 1) cout << c[j].id << " \n" [j == n - 1];

        int mn = n;
        F(j, 0, n - 1) {
            if(vst[b[j].id]) continue;
            if(mn <= pos2[b[j].id]) ok[b[j].id] = 1;
            mn = min(mn, pos2[b[j].id]);
        } mn = n;
        F(j, 0, n - 1) {
            if(vst[c[j].id]) continue;
            if(mn <= pos1[c[j].id]) ok[c[j].id] = 1;
            mn = min(mn, pos1[c[j].id]);
        } 
        F(j, 0, n - 1) if(! ok[j] && ! vst[j]) res ++;
        // cout << res << "\n";
    }

    cout << res + 1 << "\n";
}

signed main() {
    ios::sync_with_stdio(false);
    cin.tie(0);
    sol();
    return 0;
}
/*
7
1 4
4 0
2 3
3 1
3 5
0 0
2 4

*/