#include <fstream>
#include <set>
#include <cmath>  ///pentru abs()
///Varianta 3
using namespace std;
const double EPS = 1e-5;

struct Punct
{
    double x, y;

    Punct(double x = 0.0, double y = 0.0): x(x), y(y) {}

    bool operator<(const Punct &A) const
    {
        if(abs(x - A.x) > EPS)
            return x < A.x;
        if(abs(y - A.y) > EPS)
            return y < A.y;
        return 0;
    }

};

int N;
Punct P[1001];
set<Punct> S;

ifstream f("patrate3.in");
ofstream g("patrate3.out");

void solve()
{
    Punct M, A, B;
    int nrp = 0;
    for(int i = 1; i < N; i++)
        for(int j = i + 1; j <= N; j++) ///Punctele P[i] si P[j] formeaza o diagonala
        {
            M.x = (P[i].x + P[j].x) / 2;
            M.y = (P[i].y + P[j].y) / 2;
            A.x = M.x - P[j].y + M.y;
            A.y = M.y + P[j].x - M.x;
            B.x = M.x + P[j].y - M.y;
            B.y = M.y - P[j].x + M.x ;
            if(S.find(A) != S.end() && S.find(B) != S.end())
                nrp++;
        }
    g << nrp / 2;
}

int main()
{
    f >> N;
    for(int i = 1; i <= N; i++)
    {
        f >> P[i].x >> P[i].y;
        S.insert(P[i]);
    }
    solve();
    f.close();
    g.close();
    return 0;
}