#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 long long db;
const db eps = 0;
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);}
};
db dis(point A, point B) {return sqrt((A.x - B.x) * (A.x - B.x) + (A.y - B.y) * (A.y - B.y));}
typedef point vct;
db cross(point A, point B) {return A.x * B.y - A.y * B.x;}
db dot(vct A, vct B) {return A.x * B.x + A.y * B.y;}
db len(vct A) {return sqrt(dot(A, A));}
db len2(vct A) {return dot(A, A);}
db angle(vct A, vct B) {return acos(dot(A, B) / len(A) / len(B));}
db cross(vct A, vct B) {return A.x * B.y - A.y * B.x;}
db area2(point A, point B, point C) {return fabs(cross(B - A, C - A));} //平行四边形面积
bool get_region(point a) {return a.y <= 0 && (a.x < 0 || a.y < 0);}
point o = {0, 0, 0};
bool get_region(point a) {return a.y <= 0 && (a.x < 0 || a.y < 0);}
bool cmp1(point a, point b) {
point p = a - o, q = b - o;
int r1 = get_region(p), r2 = get_region(q);
if(r1 != r2) return r1 < r2;
if(cross(p, q) == 0) return dot(p, p) < dot(q, q);
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;
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];
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(), cmp1);
reverse(c.begin(), c.end());
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;
}
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) pos1[b[j].id] = j;
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;
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 + 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
*/