#include<bits/stdc++.h>
using namespace std;
#define d double
d x[1010], y[1010],n,rs;
map<d,int> m;
int main(){
	ifstream cin("trapez.in");
	ofstream cout("trapez.out");
	cin >> n;
	for (int i=0;i<n;i++)cin>>x[i]>>y[i];
	for (int i=0;i<n;i++)for(int j=i+1;j<n;j++)m[d((x[i]-x[j])/(y[i]-y[j]))]++;
	for(map<d,int>::iterator i=m.begin();i!=m.end();i++)
		{d o=i->second;rs += o*(o-1)/2;}
	cout << rs;
}