#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;
int main()
{   cin>>n;
    for(int i=1;i<=n;++i) cin>>a[i]>>b[i];
    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;
    return 0;
}