#include <bits/stdc++.h>
using namespace std;
ifstream f("trapez.in");
ofstream g("trapez.out");
int n, i, paralele=1, trapez,  j,nr;
double pante[1000001];
struct punct
{
    double x,y;
};
punct v[1001];
int main()
{   f>>n;
    for(i=1; i<=n; i++)
        f>>v[i].x>>v[i].y;
    for(i=1; i<n; i++)
        for(j=i+1; j<=n; j++)
            if(v[i].x!=v[j].x*(-1))
                pante[++nr] = (1.0*(v[j].y-v[i].y))/(1.0*(v[j].x-v[i].x));
    sort(pante+1, pante+nr+1);
    for(i=2; i<=n; i++)
        if(pante[i]==pante[i-1])
            paralele++;
        else {
            trapez = trapez + paralele*(paralele-1)/2;
            paralele = 1;
             }
    trapez = trapez + paralele*(paralele-1)/2;
    g << trapez;
    return 0;
}