#include <iostream>
#include <fstream>
#include <algorithm>
#include <cmath>
using namespace std;
const double EPS = 1e-5;

struct Punct
{
    double x, y;
};

int n;
Punct P[1001];

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

int egal(double a, double b)
{
    double d = a - b;
    if(d < -EPS) return -1;
    if(d > +EPS) return +1;
    return 0;
}

int egal(const Punct &A, const Punct &B)
{
    int ex = egal(A.x, B.x),
        ey = egal(A.y, B.y);
    if(ex == 0) return ey;
    return ex;
}

bool cmp(const Punct &A, const Punct &B)
{
    return egal(A, B) < 0;
}

bool cautbin(const Punct &A)
{
    int st = 1, dr = n;
    while(st <= dr)
    {
        int m = (st + dr) / 2,
            e = egal(P[m], A);
        if(e == 0)
            return 1;
        if(e == 1)
            dr = m - 1;
        else
            st = m + 1;
    }
    return 0;
}

void solve()
{
    Punct A, B;
    int nrp = 0;
    for(int i = 1; i < n; i++)
        for(int j = i + 1; j <= n; j++)
        {
            A.x = P[i].x - P[j].y + P[i].y;
            A.y = P[i].y + P[j].x - P[i].x;
            B.x = P[j].x - P[j].y + P[i].y;
            B.y = P[j].y + P[j].x - P[i].x;
            if(cautbin(A) && cautbin(B))
                nrp++;
        }
    g << nrp / 2;
}

int main()
{
    f >> n;
    for(int i = 1; i <= n; i++)
        f >> P[i].x >> P[i].y;
    sort(P + 1, P + n + 1, cmp);
    solve();
    f.close();
    g.close();
}