#include <bits/stdc++.h>
#define x first
#define y second
#define NMAX 1005
using namespace std;
ifstream fin("trapez.in");
ofstream fout("trapez.out");
typedef pair < int , int > point;

vector < long double > panta;

point v[NMAX],aux[NMAX];

int n,cnt,rasp;
long double raport,sus,jos;

int main()
{
    fin>>n;
    for(int i=1;i<=n;i++)
    {
        fin>>v[i].x>>v[i].y;
        for(int j=1;j<i;j++)
        {
            if(v[i].x!=v[j].x)
            {
                sus=v[i].y-v[j].y;
                jos=v[i].x-v[j].x;
                raport=sus/jos;
            }
            else raport=1e9;
            panta.push_back(raport);
        }
    }
    sort(panta.begin(),panta.end());
    n=panta.size();
    cnt=1;
    for(int i=1;i<=n;i++)
    {
        if(panta[i]==panta[i-1])cnt++;
        else
        {
            rasp+=(cnt*(cnt-1)/2);
            cnt=1;
        }
    }
    fout<<rasp;
}