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.*;

public class NumberOfTriplets {

    public static void main(String[] args) {
        Scanner inp = new Scanner(System.in);
        
        int n=inp.nextInt();
        Points arr[] = new Points[n];
        Map<Points,Integer> mymap = new HashMap<Points, Integer>();
        
        for(int i=0;i<n;i++) {
            arr[i] = new Points();
            arr[i].x = inp.nextInt();
            arr[i].y = inp.nextInt();
            mymap.put(arr[i], 1);
        }
        
        Points t = new Points();
        
    
        int count=0;
        for(int i=0;i<n;i++)
        {
            for(int j=i+1;j<n;j++)
            {
                if( ((arr[i].x+arr[j].x)%2==0) && (arr[i].y+arr[j].y)%2==0 )
                {
                    t.x = (arr[i].x+arr[j].x)/2;
                    t.y = (arr[i].y+arr[j].y)/2;
                    if(mymap.get(t)!= null)
                        count++;
                }
            
                
            }
        }
        
        System.out.println(count);


    }

}


class Points {
    int x;
    int y;
    
    public boolean equals(Object o) {
        
        if (o == this) {
            return true;
        }
        Points c = (Points) o;
        return (c.x==this.x && c.y==this.y);     
    }
    
    public int hashCode(){
    return 2000*x+y;
    }
    
    
    
    
    
    
    
    
    
    
    
}