#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[1001];

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;
}