#include <fstream>
#include <algorithm>
#define VAL 1005
#define F first
#define S second

using namespace std;

ifstream fin("patrate3.in");
ofstream fout("patrate3.out");

int N, ans, i, j;
double H, L;
pair <double, double> pct, P1, P2;
pair <double, double> P[VAL];

bool Binary_Search(pair <double, double> pct)
{
    int be=1, en=N;
    int mid;
    while (be<=en)
    {
        mid=(be+en) / 2;
        if (P[mid].F==pct.F && P[mid].S==pct.S)
          return true;
        else
        {
            if (P[mid].F<pct.F || (P[mid].F==pct.F && P[mid].S<pct.S))
              be=mid+1;
            if (P[mid].F>pct.F || (P[mid].F==pct.F && P[mid].S>pct.S))
              en=mid-1;
        }
    }
    return false;
}

int main()
{
    fin >> N;
    for (i=1; i<=N; i++)
      fin >> P[i].F >> P[i].S;
    sort(P+1, P+N+1);
    for (i=1; i<N; i++)
    {
        for (j=i+1; j<=N; j++)
        {
            pct.F=(P[i].F+P[j].F) / 2;
            pct.S=(P[i].S+P[j].S) / 2;
            H=pct.F-P[i].F;
            L=pct.S-P[i].S;
            P1.F=pct.F-L;
            P1.S=pct.S+H;
            P2.F=pct.F+L;
            P2.S=pct.S-H;
            if (Binary_Search(P1)==true && Binary_Search(P2)==true)
              ans++;
        }
    }
    fout << ans / 2 << '\n';
    fin.close();
    fout.close();
    return 0;
}