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.Collections;
import java.util.Comparator;
import java.util.Scanner;


public class Main {
    
    class Point implements Comparator<Point>, Comparable<Point>{
        public int x, y;

        @Override
        public int compare(Point o1, Point o2) {
            if( o1.x<o2.x || ( o1.x==o2.x&& o1.y<o2.y) )
                return -1;
            if( o1.x==o2.x && o1.y==o2.y ) 
                return 0;
            return 1;
        }

        @Override
        public int compareTo(Point arg0) {
            return compare(this, arg0);
        }
    };
    
    static int mod=1000000007;
    void run(){
        Scanner cin = new Scanner(System.in);
        while( cin.hasNext() ){
            int n=cin.nextInt();
            Point[] points=new Point[n];
            for(int i=0;i<n;i++){
                points[i]=new Point();
                points[i].x=cin.nextInt();
                points[i].y=cin.nextInt();
            }
            Arrays.sort(points);
            int ans=0;
            for(int i=0;i<n;i++) {
                for(int j=i+1;j<n;j++){
                    int tx=points[j].x*2-points[i].x;
                    int ty=points[j].y*2-points[i].y;
                    Point p = new Point();
                    p.x=tx;
                    p.y=ty;
                    //System.out.println(Arrays.binarySearch(points, j, n, p));
                    if( Arrays.binarySearch(points, j, n, p) >=0 )
                        ans++;
                }
            }
            System.out.println(ans);
        }
    }
    //
    public static void main(String[] args){
        Main a = new Main();
        a.run();
    }
}
