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.io.BufferedReader;
import java.io.InputStreamReader;
import java.io.StreamTokenizer;
import java.util.TreeMap;
import java.util.TreeSet;


public class Main {
	
	public static StreamTokenizer in;
	static {in = new StreamTokenizer(new InputStreamReader(System.in));}
	public static int nextInt() throws Exception{
		in.nextToken();
		return (int)in.nval;
	}
	//public static BufferedReader in;
	//static {in = new BufferedReader(new InputStreamReader(System.in));}
	private class Point implements Comparable<Point>{
		public int x;
		public int y;
		public Point(int x, int y) {
			this.x = x;
			this.y = y;
		}
		@Override
		public int compareTo(Point y) {
			if (this.x == y.x && this.y == y.y)
				return 0;
			else if (this.x > y.x || (this.x == y.x && this.y > y.y)){
				return 1;
			}
			else return -1;
		}
		
	}
	public static void main(String[] args) throws Exception {
		Main m = new Main();
		int n = nextInt();
		int[][] a = new int[n][2];
		
		TreeSet<Point> set = new TreeSet<Point>();
		for (int i = 0; i < n; i++) {
			a[i][0] = nextInt();
			a[i][1] = nextInt();
			set.add(m.new Point(a[i][0], a[i][1]));
		}
		int res = 0;
		for (int i = 0; i < n; i++) {
			for (int j = i + 1; j < n; j++) {
				if (((a[i][0] + a[j][0]) % 2 == 0) && ((a[i][1] + a[j][1]) % 2 == 0)) {
					if (set.contains(m.new Point((a[i][0] + a[j][0]) / 2, (a[i][1] + a[j][1]) / 2))){
						res++;
					}
				}
				
			}
		}
		System.out.print(res);
		System.out.flush();
	}

}
