#include <fstream>
#include <algorithm>
using namespace std;
ifstream fi("trapez.in");
ofstream fo("trapez.out");
int n,m,i,j,s,x[1001],y[1001],nr;
double p[1000001];
int main()
{fi>>n;
for(i=1;i<=n;i++) fi>>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] and i+1<=m){nr++;i++;}
  s+=(nr-1)*nr/2;
}
fo<<s;
    return 0;
}