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.Scanner;


public class B {

    public static void main(String[] argv){
        Scanner in = new Scanner ( System.in );
        int[][] t=new int[2002][2002]; long res=0;
        int n=in.nextInt(); int[] x=new int[n]; int[] y=new int[n];
        for(int i=0; i<n; i++){
            x[i]=in.nextInt(); y[i]=in.nextInt();
            t[x[i]+1000][y[i]+1000]=1;
            //System.out.println(x[i]);
            //System.out.println(y[i]);
        }
        
        for(int a=0; a<n; a++){
            for(int b=a+1; b<n; b++){
                int xa=x[a]+1000; int ya=y[a]+1000; int xb=x[b]+1000; int yb=y[b]+1000;
                int xmiddle=-1; int ymiddle=-1;
                
                   if(xa>xb){
                     if((xa-xb)%2!=0)
                         continue;
                     else
                         xmiddle=((xa+xb)/2);
                     
                   }
                   else {
                       if((xb-xa)%2!=0)
                             continue;
                         else
                             xmiddle=((xb+xa)/2);
                   }
                       
                   if(ya>yb){
                             if((ya-yb)%2!=0)
                                 continue;
                             else
                                 ymiddle=((ya+yb)/2);
                             
                   }
                   else{
                               if((yb-ya)%2!=0)
                                     continue;
                                 else
                                     ymiddle=((yb+ya)/2);
                    }
                               
                   
                    if(t[xmiddle][ymiddle]==1)
                        res++;
                       
                       
            }
        }
        System.out.println(res);
    }
}
