#include <iostream>
#include <fstream>
#include <vector>
#include <algorithm>
using namespace std;
ifstream in("trapez.in");
ofstream out("trapez.out");
#define f first
#define s second
double panta;
vector <double> v;
pair<int,int> a[1008];
int k=0,n, egal=0,s;
int main()
{
    in>>n;
    for(int i=0;i<n;i++)
    {
        in>>a[i].f>>a[i].s;
    }
    for(int i=0;i<n-1;i++)
        for(int j=i+1;j<n;j++)
        {
            panta = (double)(a[j].s - a[i].s)/(a[j].f-a[i].f);
            v.push_back(panta);
            k++;
        }
    sort(v.begin(), v.end());

    for(int i=0;i<k;i++)
    {
        egal=1;
        while(v[i]==v[i+1]&& i+1<k)
        {
            egal++;
            i++;
        }
        s+=(egal*(egal-1))/2;
    }
    out<<s;
    return 0;
}