#include <stdio.h>
#include <algorithm>
#include <cmath>
#define INF 1000000.0
using namespace std;

int n,i,j;
int A[1005],B[1005];
int q,rez,cont;
double NOU[1000005];

FILE *f,*g;

double do_it(int a, int b, double c, double d)
{
	if (a==b)
		return INF;
	return (1.0 * (d - c)) / (1.0 * (b - a));
}

bool equal(double a, double b)
{
	if (fabs(a-b)<=0.000000001)
		return 1;
	return 0;
}

int main()
{
	f=fopen("trapez.in","r");
	g=fopen("trapez.out","w");
	fscanf(f,"%d",&n);
	for (i=1;i<=n;++i)
		fscanf(f,"%d%d",&A[i],&B[i]);
	q=0;
	for (i=1;i<=n-1;++i)
		for (j=i;j<=n;++j)
		{
			q++;
			NOU[q]=do_it(A[i],A[j],B[i],B[j]);
		}
	sort(NOU+1,NOU+q+1);
	rez=cont=0;
	for (i=1;i<=q-1;++i)
		if (equal(NOU[i],NOU[i+1]))
			cont++;
		else
		{
			rez+=(cont*(cont+1)/2);
			cont=0;
		}
	fprintf(g,"%d\n",rez);
	fclose(f);
	fclose(g);
	return 0;
}