#include<iostream>
#include <bits/stdc++.h>
#define int long long 
#include<algorithm>
#include<cstdio>
#include<cmath>
#define For(i,a,b) for(int i = a; i <= b; ++i)

using namespace std;
int n;
struct ben
{
    int x,y,id;
}p[10005],s[10005];
double check(ben a1,ben a2,ben b1,ben b2)//检查叉积是否大于0，如果是a就逆时针转到b 
{
    return (a2.x-a1.x)*(b2.y-b1.y)-(b2.x-b1.x)*(a2.y-a1.y);
}
double d(ben p1,ben p2)//两点间距离。。。 
{
    return sqrt((p2.y-p1.y)*(p2.y-p1.y)+(p2.x-p1.x)*(p2.x-p1.x));
}
bool cmp(ben p1,ben p2)//排序函数，这个函数别写错了，要不然功亏一篑 
{
    double tmp=check(p[1],p1,p[1],p2);
    if(tmp>0) 
		return 1;
    if(tmp==0&&d(p[0],p1)<d(p[0],p2)) 
		return 1;
    return 0;
}
int main()
{
#ifdef NICEGUODONG
freopen("data.in","r",stdin);
#endif	
    scanf("%d",&n);
    double mid;
    for(int i=1;i<=n;i++)
    {
        scanf("%d%d",&p[i].x,&p[i].y);
        p[i].id = i;
        if(i!=1&&p[i].y<p[1].y)//这是是去重 
        {
            mid=p[1].y;p[1].y=p[i].y;p[i].y=mid;
            mid=p[1].x;p[1].x=p[i].x;p[i].x=mid;
        }
    } 
    sort(p+2,p+1+n,cmp);//系统快排 
    s[1]=p[1];//最低点一定在凸包里 
    int cnt=1;
    for(int i=2;i<=n;i++)
    {
        while(cnt>1&&check(s[cnt-1],s[cnt],s[cnt],p[i])<=0) //判断前面的会不会被踢走，如果被踢走那么出栈
			cnt--;
        cnt++;
        s[cnt]=p[i];
    }
    s[cnt+1]=p[1];//最后一个点回到凸包起点
    vector<int> Mark(n + 1);
    For(i,1,cnt + 1){
        Mark[s[i].id] = 1;
    }
int ans = 1;
    for(int i = 1; i <= n; ++i){
        vector<pair<long double,int>> a;
        if(Mark[p[i].id]) continue;
        for(int j = 1; j <= n; ++j){
            if(i == j) continue;
            a.push_back(make_pair(atan2(p[j].x - p[i].x,p[j].y - p[i].y),p[j].id));
        }
        sort(a.begin(),a.end());
        for(int i = 0;i < (int)a.size(); ++i)
            if(Mark[a[i].second] && Mark[a[(i + 1) % a.size()].second]){
ans++;
            }
    }
    cout << ans << '\n';
    // printf("%.2lf\n",ans);
    return 0;
}

cc1plus: error: ‘::main’ must return ‘int’
answer.code: In function ‘int main()’:
answer.code:37:13: warning: format ‘%d’ expects argument of type ‘int*’, but argument 2 has type ‘long long int*’ [-Wformat=]
   37 |     scanf("%d",&n);
      |            ~^  ~~
      |             |  |
      |             |  long long int*
      |             int*
      |            %lld
answer.code:41:17: warning: format ‘%d’ expects argument of type ‘int*’, but argument 2 has type ‘long long int*’ [-Wformat=]
   41 |         scanf("%d%d",&p[i].x,&p[i].y);
      |                ~^    ~~~~~~~
      |                 |    |
      |                 int* long long int*
      |                %lld
answer.code:41:19: warning: format ‘%d’ expects argument of type ‘int*’, but argument 3 has type ‘long long int*’ [-Wformat=]
   41 |         scanf("%d%d",&p[i].x,&p[i].y);
      |                  ~^          ~~~~~~~
      |                   |          |
      |                   int*       long long int*
      |                  %lld
answer.code:37:10: warning: ignoring return value of ‘int scanf(const char*, ...)’ declared with attribute ‘warn_unused_result’ [-Wunused-result]
   37 |     scanf("%d",&n);
      |     ~~~~~^~~~~~~~~
answer.code:41:14: warning: ignoring return value of ‘int scanf(const char*, ...)’ declared with attribute ‘warn_unused_result’ [-Wunused-result]
   41 |         scanf("%d%d",&p[i].x,&p[i].y);
      |         ~~~~~^~~~~~~~~~~~~~~~~~~~~~~~