#include<stdio.h>
#include<algorithm>
using namespace std;

double u[500001];

int main()
{
	freopen ("trapez.in", "r", stdin);
	freopen ("trapez.out", "w", stdout);
	int i, j, n, v[1001], b[1001], trapez=0;

	double balmus, stan, ;
	int z;
	
	scanf("%d ", &n);
	
	for(i=1; i<=n; i++){
		scanf("%d %d", &v[i], &b[i]);
	}
	
	for(i=1; i<=n; i++){
		for(j=i+1; j<=n; j++){
			balmus=b[i]-b[j];
			stan=v[i]-v[j];
			u[z]=balmus/stan;
			z++;
		}
	}
	
	sort(u+1, u+z+1);
	
	for(i=2; i<=z; i++){
		if(u[i]==u[i-1]){
			trapez++;
		}
	}
	printf("%d ", trapez*(trapez-1)/2);
	return 0;
}