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


/*
 *   
 *   Date: 07 September 2019
 *   Time: 01:03:00
*/
import java.io.*; 
import java.util.*;


   
public class triplet 
{
    public static void main(String[] args) throws NumberFormatException, IOException
    { 
        Scanner sc=new Scanner(System.in);
        int n=sc.nextInt();
        int a[][]=new int[n][n];
        boolean b[][]=new boolean[2001][2001];
        for(int i=0;i<n;i++){
        	for(int j=0;j<2;j++){
        		a[i][j]=sc.nextInt();
        	}
        }
        for(int i=0;i<n;i++){
        	b[a[i][0]+1000][a[i][1]+1000]=true;
        }
        int k=0;
        for(int i=0;i<n;i++){
        	for(int j=i+1;j<n;j++){
        		int midx=a[i][0]+a[j][0];
        		int midy=a[i][1]+a[j][1];
        		if(midx%2==0 && midy%2==0){
        			midx=midx/2;
        			midy=midy/2;
        			if(b[midx+1000][midy+1000]){
        				k++;
        			}
        		}
        	}
        }
        System.out.println(k);

    } 
} 
 
 
 
