#include <iostream>
#include <fstream>
#include <algorithm>
using namespace std;
struct puncte_trapez
{
    int x,y;
}v[1001];
struct pante_trapez
{
    double panta;
    int dif1,dif2;
}a[1000001];
bool comparare(pante_trapez A,pante_trapez B)
{
    return A.panta<B.panta;
}
int main()
{
    ifstream fin("trapez.in");
    ofstream fout("trapez.out");
    int N,i,j,start=0,nr,counter=0;
    fin>>N;
    for(i=1;i<=N;i++)
    {
        fin>>v[i].x>>v[i].y;
    }
    for(i=1;i<=N;i++)
      for(j=i+1;j<=N;j++)
    {

            start++;
            a[start].dif1=v[j].x-v[i].x;
            a[start].dif2=v[j].y-v[i].y;

            a[start].panta=double(a[start].dif1)/double(a[start].dif2);


    }
    sort(a+1,a+start+1,comparare);
    for(i=1;i<=start;i++)
    {
        nr=1;
        while(i<start && a[i].panta==a[i+1].panta)
        {
            i++;
            nr++;
        }
        counter=counter+(nr*(nr-1))/2;
    }
    fout<<counter;
    fin.close();
    fout.close();
    return 0;
}