#include <fstream>
#include <algorithm>

using namespace std;

ifstream cin("trapez.in");
ofstream cout("trapez.out");
double panta[1000001];
int n,a[1001],b[1001],nr,x;

void citire()
{
  cin>>n;

  for(int i=1;i<=n;++i)
      cin>>a[i]>>b[i];

}

void rezolvare()
{
  for(int i=1;i<n;++i)
    for(int j=i+1;j<=n;++j)

     if(a[j]==a[i])
       panta[++x]=100000000;
     else
       panta[++x]=(b[i]-b[j])*1.00/(a[i]-a[j]);

  sort(panta+1,panta+x);

  int ct;
  for(int i=1;i<=x;++i)
    {  ct=1;
        while(panta[i]==panta[i+1] && i+1<=x)++i,++ct;

    nr+=ct*(ct-1)/2;
    }
    cout<<nr;

}


int main()
{
 citire();
 rezolvare();

    return 0;
}