#include <fstream>
#include <algorithm>
#define value 20000
using namespace std;
ifstream f("trapez.in");
ofstream g("trapez.out");
struct{

double x, y;

}a[value];


int n, m, j, i, d[value], k, h, sol;
int main()
{
    f >> n;
    f >> a[1].x >> a[1].y;

    for( i = 2 ; i <= n ; i++ )
    {
        f >> a[i].x >> a[i].y;
        for( j = 1 ; j <= i ; j++ )
        {
            if( a[i].x != a[j].x )
            {
                k++;
                d[k] = (a[i].y-a[j].y)/(a[i].x-a[j].x);
            }
        }
    }
    sort( d+1 , d+k+1);
    for( i = 1 ; i <= k ; i++ )
    {
        h = i-1;
        while ( h > 0 && d[h] == d[i] )
        {
            sol++;
            h--;
        }

    }
    g << sol << "\n";
    return 0;
}