#include <iostream>
#include <fstream>
#include <vector>
#include <algorithm>

using namespace std;

typedef long long lint;

int gcd(int a, int b)
{
    if(b == 0){
        return a;
    }
    return gcd(b, a%b);
}

struct boi{
    int a, b;
    void yeet()
    {
        cout << a << " " << b << "\n";
    }
    void susta()
    {
        int x = gcd(a, b);
        a /= x; b /= x;
    }
    void susta_reloaded()
    {
        if((a <= 0 && b <= 0) || (a <= 0 && b >= 0)){
            a = -a; b = -b;
        }
    }
};
bool operator<(const boi & lhs, const boi & rhs)
{
    return lhs.a < rhs.a || (lhs.a == rhs.a && lhs.b < rhs.b);
}
bool operator==(const boi & lhs, const boi & rhs)
{
    return lhs.a == rhs.a && lhs.b == rhs.b;
}

int trap(int a)
{
    return a*(a-1)/2;
}

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

vector<boi> points;
vector<boi> parale;

int main()
{
    int n;
    fin >> n;
    for(int i = 0; i < n; i++){
        int a, b;
        fin >> a >> b;
        points.push_back({a, b});
    }

    for(int i = 0; i < n; i++){
        boi p1 = points[i];
        for(int j = i+1; j < n; j++){
            boi p2 = points[j];
            boi ln = {p1.a - p2.a, p1.b - p2.b};

            ln.susta();
            ln.susta_reloaded();
            parale.push_back(ln);
        }
    }

    sort(parale.begin(), parale.end());
    lint sol = 0;
    boi ex = parale.front();
    int st = 0;
    for(auto ln : parale){
        if(ln == ex){
            st++;
        }else{
            sol += trap(st);
            ex = ln;
            st = 1;
        }
    }
    sol += trap(st);

    fout << sol;
    return 0;
}