#include <bits/stdc++.h>
using namespace std;
double r[1000005];
int a[1005],b[1005];
int main()
{
    freopen("trapez.in","r",stdin);
    freopen("trapez.out","w",stdout);
    cin.sync_with_stdio(false);
    cin.tie(0);
    int n,m=0;
    cin>>n;
    for(int i=1; i<=n; i++)cin>>a[i]>>b[i];
    for(int i=1; i<=n; i++)
        for(int j=i+1; j<=n; j++)
            r[++m]=(double)(a[i]-a[j])/(b[i]-b[j]);
    sort(r+1,r+m+1);
    int s=0;
    for(int i=1; i<=m; i++)
    {
        int nr=1;
        while(r[i]==r[i+1] && i<=m)nr++,i++;
        s+=(nr-1)*nr/2;
    }
    ///posibil signal 8
    cout<<s<<'\n';
}