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.HashSet;
import java.util.Scanner;

public class KK {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        Point[] ans = new Point[n];
        HashSet<Point> ch = new HashSet<Point>();

        for (int i = 0; i < n; i++) {
            int xx = sc.nextInt();
            int yy = sc.nextInt();
            Point ff = new Point(xx, yy);
            ch.add(ff);
            ans[i] = ff;
        }
        int out = 0;
        for (int i = 0; i < n; i++) {
            for (int j = i + 1; j < n; j++) {
                if ((ans[i].x + ans[j].x) % 2 == 0
                        && (ans[i].y + ans[j].y) % 2 == 0) {
                    Point kk = new Point((ans[i].x + ans[j].x) / 2,
                            (ans[i].y + ans[j].y) / 2);
                    if (ch.contains(kk)) {
                        out++;
                    }
                
                }
            }
        }

        System.out.println(out);
        sc.close();
    }
}


class Point {
    Point(int x, int y) {
        this.x = x;
        this.y = y;
    }
    @Override
    public boolean equals(Object obj) {
        Point t = (Point)obj;
        return (this.x == t.x && this.y == t.y);
    }   
    int x;
    int y;
    @Override
    public int hashCode() {
        // TODO Auto-generated method stub
        return ((Integer)(x*1000+y)).hashCode();
    }
    
}