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.Map;
import java.util.Scanner;
import java.util.TreeMap;

/**
 * Created by IntelliJ IDEA.
 * User: Linkov Mikl
 * Date: 20.04.12
 * Time: 18:49
 * To change this template use File | Settings | File Templates.
 */
public class ProblemTwo {
    static class Position implements Comparable<Position> {
        private int x;
        private int y;

        public Position(int x, int y) {
            this.x = x;
            this.y = y;
        }

        public int compareTo(Position position) {
            if (position.x != x) {
                return position.x - x;
            }
            return position.y - y;
        }

    }
    public static void main(String [] args) {
        Scanner scanner = new Scanner(System.in);

        Map<Position, Integer> map = new TreeMap<Position, Integer>();

        int n = scanner.nextInt();

        int [] x = new int[n];
        int [] y = new int[n];

        for (int i = 0; i < n; i++) {
            int X = scanner.nextInt();
            int Y = scanner.nextInt();

            Position position = new Position(X, Y);

            x[i] = X;
            y[i] = Y;

            if (!map.containsKey(position)) {
                map.put(position, 1);
            } else {
                int count = map.get(position) + 1;

                map.put(position, count + 1);
            }
        }

        int answer = 0;

        for (int i = 0; i < n; i++) {
            for (int j = i + 1; j < n; j++) {

                if ((x[i] + x[j]) % 2 != 0) {
                    continue;
                }

                if ((y[i] + y[j]) % 2 != 0) {
                    continue;
                }

                int X = (x[i] + x[j]) / 2;
                int Y = (y[i] + y[j]) / 2;


                if (map.containsKey(new Position(X, Y))) {
                    answer += map.get(new Position(X, Y));
                }

            }
        }
        System.out.println(answer);
    }
}
