#include <iostream>

#include <fstream>

using namespace std; 

ifstream f("trapez.in"); 
ofstream g("trapez.out"); 

unsigned long long v[1001], w[1001], i,j, N, t, k, piv, nr, perechi; 

float a[1000001] , aux; 









int main()

{
	f >> N;

	for (i = 0; i <= N - 1; i++) {

		f >> v[i];

		f >> w[i];

	}

	t = 0;

	for (i = 0; i <= N - 2; i++) for (j = i + 1; j <= N - 1; j++) {
		if (w[i] != w[j])

			a[t] = (v[i] - v[j]) / (w[i] - w[j]);

		else a[t] = 2000001;



		t++;


	}

	t--;


	for (i = 0; i <= t - 1; i++) for (j = i + 1; j <= t; j++) if (a[i] > a[j]) { aux = a[i]; a[i] = a[j]; a[j] = aux; }


	k = 0; piv = 0; perechi = 0;

	while (k <= t) {

		nr = 0;

		while (a[k] == a[piv] && k <= t)   { nr++; k++; }

		piv = k;

		perechi = perechi + (nr * (nr - 1)) / 2;

	}


	g << perechi;

	f.close(); 

	g.close(); 
	
	
	return 0;



}