#include <bits/stdc++.h>
#define EPS 0.0000001

using namespace std;

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

struct point{
	double x, y;
	bool operator < (const point& other) const {
		return (abs(x - other.x) < EPS ? y < other.y - EPS : x < other.x - EPS);
	}
};

int n, cnt;
point P[1010];
set <point> h;

int main(){
	in >> n;
	for(int i = 1; i <= n; i++)
		in >> P[i].x >> P[i].y, h.insert(P[i]);
	sort(P + 1, P + n + 1);
	for(int i = 1; i < n; i++){
		for(int j = i + 1; j <= n; j++){
			point M, A, B;
			M.x = (P[i].x + P[j].x) / 2;
			M.y = (P[i].y + P[j].y) / 2;
			double H = abs(P[j].y - M.y);
			double L = abs(P[j].x - M.x);
			if(P[j].y < P[i].y)
				H = -H;
			A.x = M.x - H;
			A.y = M.y + L;
			B.x = M.x + H;
			B.y = M.y - L;
			if(h.count(A) && h.count(B))
				cnt++;
		}
	}
	out << cnt / 2;
	return 0;
}