#include <fstream>
#include <unordered_map>
using namespace std;

int main() {
    ifstream fin("trapez.in");
    ofstream fout("trapez.out");

    int n, s = 0, xd;
    double m;
    int x[1000], y[1000];
    unordered_map<double, int> um;
    fin >> n;
    for (int i = 0; i < n; i++) {
        fin >> x[i] >> y[i];
        for (int j = 0; j < i; j++) {
            xd = x[j] - x[i];
            if (xd != 0) 
                m = (double)(y[j] - y[i]) / xd;
            else 
                m = -1;
            s += um[m]++;
        }
    }
    fout << s;
    return 0;
}