#include <iostream>
#include <fstream>
#include <cmath>
#include <vector>
using namespace std;
#define maxn 10001
#define mod 666013
int n, answer=0;
vector<int> h[mod];
double err=1/10000;
struct point
{
    double x, y;
};
point p[maxn];
int get_hash(point m)
{
    int ans;
    ans=(int)(m.x+m.y);
    if (ans<0) ans=-ans;
    ans=ans%mod;
    return ans;
}
bool finder(point m)
{
    int hh=get_hash(m), i;
    int a, b, c, d;
    c=(int)m.x*10000;
    d=(int)m.y*10000;
    for (i=0;i<h[hh].size();i++)
    {
    a=(int)p[h[hh][i]].x*10000;
    b=(int)p[h[hh][i]].y*10000;
    if (a==c && b==d) return true;
    }
    return false;
}
int main()
{
    ifstream f("patrate3.in");
    ofstream g("patrate3.out");
    int i, j;
    point c, d, m;
    f>>n;
    for (i=0;i<n;i++)
    {
        f>>p[i].x>>p[i].y;
        h[get_hash(p[i])].push_back(i);
    }
    for (i=0;i<n-1;i++)
        for (j=i+1;j<n;j++)
        {
               m.x=(p[i].x+p[j].x)/2;
               m.y=(p[i].y+p[j].y)/2;
               c.x=-(p[i].y-m.y)+m.x;
               c.y=(p[i].x-m.x)+m.y;
               d.x=(p[i].y-m.y)+m.x;
               d.y=-(p[i].x-m.x)+m.y;
               if (finder(c) && finder(d)) answer++;
        }
    answer=answer/2;
    g<<answer<<'\n';
}