#include <fstream>
#include <algorithm>
#define nmax 1001

using namespace std;

ifstream fin("trapez.in");
ofstream fout("trapez.out");

int n,a[nmax],b[nmax],nr,r=1,rez;
double panta[nmax];

int main()
{
    int i,j;
    fin>>n;
    for(i=1; i<=n; i++)
        fin>>a[i]>>b[i];
    for(i=1; i<n; i++)
        for(j=i+1; j<=n; j++)
            panta[++nr]=1.0*(b[j]-b[i])/(a[j]-a[i]);
    sort(panta+1,panta+nr+1);
    for(i=2;i<=nr;i++)
    {
        if(panta[i]==panta[i-1])
            r++;
        else rez=rez+r*(r-1)/2,r=1;
    }
    fout<<rez+r*(r-1)/2;
    return 0;
}