#include <fstream>
#include <algorithm>
#include <cmath>
#include <vector>

using namespace std;

const double PI = 2.0 * acos(0);
const double eps = 1.0e-14;
const double INF = 2.0e9;

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

double panta[600001];

class POINT
{
public:
    double x, y;
    POINT()
    {
        x = y = 0;
    }
    POINT(double x0, double y0)
    {
        x = x0;
        y = y0;
    }
    POINT(const POINT& other)
    {
        x = other.x;
        y = other.y;
    }

    void setxy(double x0, double y0)
    {
        x = x0;
        y = y0;
    }
    double getx()
    {
        return x;
    }
    double gety()
    {
        return y;
    }
    double dist(const POINT& other)
    {
        return sqrt((x - other.x) * (x - other.x) + (y - other.y) * (y - other.y));
    }
    double calcularepanta(const POINT& other)
    {
        if (fabs(other.x - x) < eps)
            return INF;
        return (other.y - y) / (other.x - x);
    }

};

int main()
{
    int n, i, j, nr = 0, c = 1, x, y, k = 0;
    fin >> n;
    POINT p[1001];
    for (i = 0; i < n; i++)
    {
        fin >> x >> y;
        p[i].setxy(x, y);
    }
    for (i = 0; i < n - 1; i++)
        for (j = i + 1; j < n; j++)
            if (p[i].x != p[j].x * (-1))
                panta[k++] = p[i].calcularepanta(p[j]);
    sort(panta, panta + k);
    panta[-1] = -10000000;
    for (i = 0; i <= k; i++)
        if (panta[i] == panta[i - 1])
            c++;
        else
        {
            nr += (c * (c - 1)) / 2;
            c = 1;
        }
    nr += (c * (c - 1)) / 2;
    fout << nr;
    return 0;
}