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.util.ArrayList;
import java.util.List;
import java.util.Set;
import java.util.TreeSet;

/**
 * 
 */

/**
 * @author antonio081014
 * @time: Apr 20, 2012, 8:48:09 AM
 */
public class B {

    List<Pair> list;
    Set<Pair> set;

    /**
     * @param args
     */
    public static void main(String[] args) throws Exception {
	B main = new B();
	main.run();
	System.exit(0);

    }

    public void run() throws Exception {
	BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
	int n = Integer.parseInt(br.readLine());

	set = new TreeSet<Pair>();
	for (int i = 0; i < n; i++) {
	    String[] str = br.readLine().split("\\s");
	    int a = Integer.parseInt(str[0]);
	    int b = Integer.parseInt(str[1]);
	    set.add(new Pair(a, b));
	}
	list = new ArrayList<Pair>(set);

	int count = 0;
	for (int i = 0; i < n; i++) {// A
	    for (int j = i + 1; j < n; j++) {// C
		int a = list.get(i).x + list.get(j).x;
		int b = list.get(i).y + list.get(j).y;
		if (a % 2 == 0 && b % 2 == 0) {
		    Pair p = new Pair(a / 2, b / 2);
		    if (set.contains(p))
			count++;
		}
	    }
	}
	System.out.println(count);
    }
}

class Pair implements Comparable<Pair> {
    public int x;
    public int y;

    public Pair(int xx, int yy) {
	this.x = xx;
	this.y = yy;
    }

    public int compareTo(Pair p) {
	if (this.x != p.x)
	    return this.x - p.x;
	return this.y - p.y;
    }
}