#include<bits/stdc++.h>
using namespace std;
#define i64 __int128
#define db double
#define ldb long double
#define ull unsigned long long
#define ll long long
#define pb push_back
#define fi first
#define se second
#define pii pair<int,int>
#define lowbit(i) (i&-i) 
const int N = 2e5+5;
ll n,top,len,use[N],stk[N],p[N],per[N],rk[N];
struct Node{
    ll x,y;
    friend Node operator - (Node a,Node b){
        return Node{a.x-b.x,a.y-b.y};
    }
    friend Node operator + (Node a,Node b){
        return Node{a.x+b.x,a.y+b.y};
    } 
    friend ll operator * (Node a,Node b){
        return a.x*b.y-a.y*b.x;
    }
}s[N];
double degree(int i,int j){
    return atan2((s[j].y-s[i].y),(s[j].x-s[i].x));
}
bool cmp(Node a,Node b){
    if(a.x==b.x) return a.y<b.y;
    return a.x<b.x;
}
void Andrew(){
    stk[++top] = 1,use[1] = 1;
    for(int i=2;i<=n;i++){
        while(top>1 && (s[stk[top]]-s[stk[top-1]])*(s[i]-s[stk[top]])<0) use[stk[top--]] = 0; 
        stk[++top] = i,use[i] = 1;
    }
    int k = top;
    for(int i=n;i>=1;i--){
        if(use[i]) continue;
        while(top>k && (s[stk[top]]-s[stk[top-1]])*(s[i]-s[stk[top]])<=0) use[stk[top--]] = 0;
        stk[++top] = i,use[i] = 1;
    }
    while(top) p[++len] = stk[top--];
    p[len+1] = p[1];
}
int main(){
    ios::sync_with_stdio(0);
    cin.tie(0),cout.tie(0);
    cin >> n;
    for(int i=1;i<=n;i++) cin >> s[i].x >> s[i].y;
    sort(s+1,s+1+n,cmp);
    Andrew();
    int ans = 1;
    for(int u=1;u<=n;u++){
        if(use[u]) continue;
        int sz = 0;
        for(int i=1;i<=n;i++){
            if(i==u) continue;
            per[++sz] = i;
        }
        sort(per+1,per+1+sz,[&](int x,int y){return degree(u,x)<degree(u,y);});
        for(int i=1;i<=sz;i++) rk[per[i]] = i;
        for(int i=1;i<=len;i++) if(abs(rk[p[i]]-rk[p[i+1]])==1 || abs(rk[p[i]]-rk[p[i+1]])==sz-1) ans++; 
    }
    cout << ans;
    return 0;
}