#include <fstream>
#include <algorithm>
using namespace std;
ifstream fin ("trapez.in");
ofstream fout("trapez.out");
double v[1000001];
int x[1001],y[1001],i,j,n,sol,nr,m;
int main()
{
    fin>>n;
    for(i=1;i<=n;i++) fin>>x[i]>>y[i];
    for(i=1;i<n;i++) for(j=i+1;j<=n;j++) v[++m]=1.0*(x[i]-x[j])/(y[i]-y[j]);
    sort(v+1, v+m+1);
    for(i=1;i<=m;i++){
        nr=1;
        while(v[i]==v[i+1]&&i+1<=m) nr++,i++;
        sol+=(nr-1)*nr/2;
    }
    fout<<sol;
    fin.close();
    fout.close();
    return 0;
}