#include <fstream>
#include <algorithm>

using namespace std;

ifstream f ("trapez.in");
ofstream g ("trapez.out");

int n,m,i,j,s,x[1001],y[1001],nr;
double p[1000001];

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+1<=m)
        {
            nr++;
            i++;
        }
        s+=(nr-1)*nr/2;
    }
    g<<s;
    return 0;
}