You are given n points on a plane. All the points are distinct and no three of them lie on the same line. Find the number of parallelograms with the vertices at the given points.

Input

The first line of the input contains integer n (1 ≤ n ≤ 2000) — the number of points.

Each of the next n lines contains two integers (xi, yi) (0 ≤ xi, yi ≤ 109) — the coordinates of the i-th point.

Output

Print the only integer c — the number of parallelograms with the vertices at the given points.

Example

Input

4
0 1
1 0
1 1
2 0


Output

1


import java.util.Arrays;
import java.util.Comparator;
import java.util.Scanner;


public class Main {
	static Scanner cin = new Scanner(System.in);
	public static void main(String[] argvs){
		int N = cin.nextInt();
		Point[] a = new Point[N];
		for(int i = 0; i < N; i++){
			a[i] = new Point();
			a[i].x = cin.nextDouble();
			a[i].y = cin.nextDouble();
			//a[i].Put();
		}
		Point[] b = new Point[N * (N + 1)/2];
		int tp = 0;
		for(int i = 0; i < N*(N + 1)/2; i++)
				b[i] = new Point();
		for(int i = 0; i < N; i++){
			for(int j = i + 1; j < N; j++){
				if(a[i].x == a[j].x && a[i].y == a[j].y)
					continue;
				b[tp++] = Point.getp(a[i], a[j]);
			}
		}
		
		Arrays.sort(b, 0, tp, new PointComparator());
//		System.out.println("tp = " + tp);
		int ans = 0, cnt = 1;
		for(int i = 1; i < tp; i++){
		//	System.out.println(b[i].x + " " + b[i].y);
			if(b[i].x == b[i - 1].x && b[i].y == b[i - 1].y){
				cnt++;
			}
			else{
				ans += cnt * (cnt - 1) / 2;
				cnt = 1;
			}
		}
		System.out.println(ans);
	}
}

class Point{
	static Scanner cin = new Scanner(System.in);
	public double x, y;
	public void Put(){
		x = cin.nextInt();
		y = cin.nextInt();
	//	System.out.println("***" + this.x + " " + this.y);
	}
	static Point getp(Point a, Point b){
		Point c = new Point();
		c.x = (a.x + b.x) / 2;
		c.y = (a.y + b.y) / 2;
	//	System.out.println("***" + c.x + " " + c.y);
		return c;
	}
}
class PointComparator implements Comparator{
	public int compare(Object x, Object y){
		Point a = (Point)x;
		Point b = (Point)y;
			if(a.x != b.x){
				if(a.x <= b.x)
					return -1;
				else
					return 1;
			}
			else{
				if(a.y <= b.y)
					return -1;
				else
					return 1;
			}
	}
}