#include <bits/stdc++.h>
using namespace std;

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

double eroare=0.0001;
int n, nr;

struct punct
{
    double x,y;
}a, b ,v[1010];

bool compara(punct a, punct b)
{
    if(abs(a.x-b.x) < eroare)
        return a.y<b.y;
    return a.x<b.x;
}
bool cauta(punct a)
{
    int mijloc, stanga, dreapta;
    stanga=1, dreapta=n;
    while(stanga<=dreapta)
    {
        mijloc=(stanga+dreapta)/2;
        if(abs(v[mijloc].x-a.x)<eroare && abs(v[mijloc].y-a.y)<eroare)
            return true;
        if(compara(v[mijloc],a))
            stanga=mijloc+1;
        else
            dreapta=mijloc-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,compara);
    for(int i=1 ; i<n ; i++)
        for(int j=i+1 ; j<=n ; j++)
        {   a.x=v[i].x+v[i].y-v[j].y;
            a.y=v[i].y+v[j].x-v[i].x;
            b.x=v[j].x+v[i].y-v[j].y;
            b.y=v[j].y+v[j].x-v[i].x;
            if(cauta(a) && cauta(b))
                nr++;
        }
    fout<<nr/2;
}