10
-2 1
2 -2
-1 -2
0 0
2 -1
0 -2
2 2
0 2
-1 -1
1 -2
 40
-8 24
2 -1
1 -18
72 -70
5 -4
-308 436
-19 40
36 -35
-178 265
-1 2
-7 30
-1 0
3 -2
200 -285
17 -16
-35 74
0 -4
-86 106
-1 4
-7 6
0 1
-5 4
-2 3
6 -5
-4 5
181 -262
76 -118
0 0
-7 18
-58 104
-5 6
-6 12
-3 4
1 0
11 -10
-86 130
-3 6
153 -236
-183 270
-33 64
 5
0 -1
0 -2
0 -3
0 -4
0 -5
 10
0 1
-1 -1
1 1
-1 0
1 -1
-2 -1
-2 2
-2 0
0 -2
0 -1
 20
-1 18
-2 5
-5 4
2 -33
9 -18
0 0
11 -22
2 0
-1 2
-4 41
1 6
1 -2
6 -12
0 1
-3 6
3 -6
3 -8
-1 4
2 -5
1 0
 10
2 1
-1 0
-2 -1
-1 1
0 2
2 -2
0 0
-2 -2
0 -2
-2 1
 20
-3 -3
0 4
-3 1
1 1
-1 2
-4 4
3 -1
-3 0
0 2
4 0
2 3
2 4
4 -3
-4 3
-1 1
1 3
-2 4
1 -2
1 -1
3 0
 3
0 0
0 -1
0 1
 10
2 1
-1 1
0 0
-3 1
-2 -3
-1 -2
-1 -1
1 2
3 -2
0 -2
 3
3 3
1 2
1 1
 4
0 0
1 0
2 0
3 0
 9
1 1
1 0
0 1
0 0
-1 0
-1 1
-1 -1
1 -1
0 -1
 7
1 1
-1 -1
1 0
0 1
-1 0
0 -1
0 0

4
 57
 4
 5
 21
 4
 10
 1
 1
 0
 2
 8
 3

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

public class CROC_1012_B {
	static class point implements Comparable<point>{
		int x,y;
		public int compareTo(point arg0) {
			if(this.x>arg0.x || this.x==arg0.x && this.y>arg0.y) return 1;
			return 0;
		}
		public point( int a, int b) {
			x = a; y = b;
		}
	}
	static point a[];
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();
		a= new point [n];
		for (int i = 0; i < n; i++) {
			a[i] = new point(sc.nextInt(), sc.nextInt());
		}
		Arrays.sort(a);
		int count = 0;
		for (int i = 0; i < n - 1; i++) {
			for (int j = i + 1; j < n; j++) {
				if((a[i].x+a[j].x) % 2==0 && (a[i].y+a[j].y) % 2==0) {
//					System.out.println(binarySearch(0,n,new point((a[i].x+a[j].x) / 2, (a[i].y+a[j].y )/ 2)));
					if(binarySearch(0,n,new point((a[i].x+a[j].x) / 2, (a[i].y+a[j].y )/ 2))>-1){
						count++;
						
					}
				}
			}
		}
		System.out.println(count);
	}
	public static int binarySearch(int l, int r, point x){
		int m = (l+r) / 2;
		
		if(a[m].x == x.x && a[m].y == x.y) return m;
		
		if(l+1>=r) return -1;
		
		if(a[m].x < x.x || a[m].x == x.x && a[m].y < x.y) return binarySearch(m, r, x); else return binarySearch(l, m, x);
	}
}
