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 Main {

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

        int n = in.nextInt();
        Pair pairs[] = new Pair[n];


        for (int i = 0; i < n; i++) {
            int x = in.nextInt();
            int y = in.nextInt();

            pairs[i] = new Pair(x, y);
        }

        Arrays.sort(pairs);


        int count = 0;
        for (int i = 0; i < n; i++) {
            for (int j = i + 1; j < n; j++) {
                int sum1 = pairs[i].x + pairs[j].x;
                int sum2 = pairs[i].y + pairs[j].y;

                if(sum1 % 2 == 0 && sum2 % 2 == 0){
                    int x = sum1 / 2;
                    int y = sum2 / 2;

                    if(Arrays.binarySearch(pairs , new Pair(x , y)) >= 0){
                        count ++;
                    }
                }
            }
        }


        System.out.println(count);
    }


    static class Pair implements Comparable<Pair> {
        int x, y;

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

        @Override
        public int compareTo(Pair pair) {
            if (pair.x < this.x || (pair.x == this.x && pair.y < this.y))
                return 1;
            else if (pair.x == this.x && pair.y == this.y)
                return 0;
            else
                return -1;
        }
    }

}
