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.io.BufferedReader;
import java.io.InputStreamReader;
import java.util.ArrayList;
import java.util.Comparator;
import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;
import java.util.TreeSet;
import java.util.Map.Entry;
import java.util.Set;
import java.util.StringTokenizer;


public class Main {
    public static void main(String[] args) throws Exception {
        BufferedReader in = new BufferedReader(new InputStreamReader(System.in));
        
        int n = Integer.parseInt(in.readLine());
        
        ArrayList<Pair> A = new ArrayList<Pair>();
        TreeSet<Pair> set = new TreeSet<Pair>(new MyCmp());
        
        for (int i = 0 ; i < n ; i++) {
            StringTokenizer st = new StringTokenizer(in.readLine());
            
            Pair p = new Pair(Integer.parseInt(st.nextToken()),
                              Integer.parseInt(st.nextToken()));
            
            A.add(p);
            set.add(p);
        }
        
        int result = 0;
        
        for (int i = 0 ; i < n ; i++) {
            for (int j = i + 1 ; j < n ; j++) {
                int nx = A.get(i).x + A.get(j).x;
                int ny = A.get(i).y + A.get(j).y;
                
                if (nx % 2 != 0 || ny % 2 != 0) {
                    continue;
                } else {
                    nx /= 2;
                    ny /= 2;
                    
                    if (set.contains(new Pair(nx, ny))) {
                        result++;
                    }
                }
            }
        }
        
        System.out.println(result);
    }
    
    static class Pair {
        int x, y;
        
        Pair(int a, int b) { this.x = a; this.y = b; }
    }
    
    static class MyCmp implements Comparator<Pair> {
        public int compare(Pair A, Pair B) {
            if (A.x < B.x || (A.x == B.x && A.y < B.y)) return -1;
            else if (A.x == B.x && A.y == B.y) return 0;
            else return 1;
        }
    }
}
