#include <iostream>
#include <fstream>
#include <set>
#include <cmath>

using namespace std;
const double EPS=1e-5;

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

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;

    void solve()
    {
        Punct M,A,B;
        int nrp=0;
        for(int i=1;i<N;i++)
            for(int j=i+1;j<=N;j++)
        {
             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;
}