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.*;
import java.io.*;

public class Solution{

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

        int n = sc.nextInt();
        int[][] points = new int[n][2];
        int res = 0;
        boolean[][] mid = new boolean[2001][2001];
        int ptr = 0;
        
        while(ptr < n){
            int val1 = sc.nextInt();
            int val2 = sc.nextInt();
            
            points[ptr][0] = val1 + 1000;
            points[ptr][1] = val2+ 1000;
            mid[val1 + 1000][val2 + 1000] = true;
            ptr += 1;
        }
        
        
        for(int i = 0 ; i < n - 1 ; i++){
            int x1 = points[i][0];
            int y1 = points[i][1];
            
            
            for(int j = i + 1 ; j < n ; j++) {
                int x2 = points[j][0];
                int y2 = points[j][1];
                
                //System.out.println( x1 +" " + y1+ " "+x2 +" " + y2);
                double midx1 = (x1 + x2) / 2.0;
                double midy1 = (y1 + y2) / 2.0;
                
                int midx2 = (x1 + x2) / 2;
                int midy2 = (y1 + y2) / 2;
                
                if(midx1 == midx2 && midy1 == midy2){
                    if(mid[midx2][midy2] == true){
                        res += 1;
                    }
                }
                //System.out.println(midx +" " + midy);
                
            }
            
        }
        System.out.println(res);
       
        
        
        
        
        
          
      }
      
     
}