#include <bits/stdc++.h>
using namespace std;
ifstream f("trapez.in");
ofstream g("trapez.out");
int n,m,i,j,s,nr,x[1<<10],y[1<<10];
double p[1<<19];
int main()
{
    f>>n;
    for(i=1;i<=n;++i) f>>x[i]>>y[i];
    for(i=1;i<=n;++i)
        for(j=i+1;j<=n;++j)
            p[++m]=(double)(x[i]-x[j])/(y[i]-y[j]);
    sort(p+1,p+m+1);
    for(i=1;i<=m;++i)
    {
        nr=1;
        while(p[i]==p[i+1]&&i<m) nr++,i++;
        s+=(nr-1)*nr/2;
    }
    g<<s;
    return 0;
}