#include <bits/stdc++.h>
using namespace std;
ifstream fin("patrate3.in");
ofstream fout("patrate3.out");
int n;
const double eps = 0.0001;
struct Point
{
    double x, y;
}v[1005];

bool cmp(Point a, Point b)
{
    if (abs(a.x - b.x) < eps) return a.y < b.y;
    return a.x < b.x;
}

bool Exista(Point a)
{
    int st = 1, dr = n;
    while (st <= dr)
    {
        int mid = (st + dr) / 2;
        if (abs(a.x - v[mid].x) < eps && abs(a.y - v[mid].y) < eps) return true;
        if (cmp(a, v[mid]) == true) dr = mid - 1;
        else st = mid + 1;
    }
    return false;
}

int main()
{
    fin >> n;
    for (int i = 1; i <= n; ++i)
    {
        fin >> v[i].x >> v[i].y;
    }
    sort(v + 1, v + n + 1, cmp);
    int contor = 0;
    for (int i = 1; i < n; ++i)
    {
        for (int j = i + 1; j <= n; ++j)
        {
            Point m,a,b;
            m.x=(v[i].x+v[j].x)/2;
            m.y=(v[i].y+v[j].y)/2;
            a.x= m.x - v[j].y + m.y;
            a.y= m.y + v[j].x - m.x;
            b.x= m.x + v[j].y - m.y;
            b.y= m.y - v[j].x + m.x;
            if (Exista(a) && Exista(b)) ++contor;
        }
    }
    fout << contor / 2;
    fin.close();
    fout.close();
    return 0;
}