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.IOException;
import java.io.InputStreamReader;
import java.util.StringTokenizer;
import java.util.TreeSet;


public class Triplets {
	
	static class Scanner{
		BufferedReader rd;
		StringTokenizer tk;
		public Scanner(){
			rd = new BufferedReader(new InputStreamReader(System.in));
			tk = null;
		}
		String next() throws IOException{
			while(tk == null || !tk.hasMoreTokens()){
				tk = new StringTokenizer(rd.readLine());
			}
			return tk.nextToken();
		}
		int nextInt() throws NumberFormatException, IOException{
			return Integer.valueOf(next());
		}
		double nextDouble() throws NumberFormatException, IOException{
			return Double.valueOf(next());
		}
	}
	
	static class Point implements Comparable<Point>{
		int x,y;
		public Point(int xx, int yy){
			x = xx;
			y = yy;
		}
		public Point add(Point o){
			return new Point(x + o.x, y + o.y);
		}
		boolean isvalid(){
			return (x % 2 == 0) && (y % 2 ==0);
		}
		public Point mid(){
			return new Point(x / 2, y / 2);
		}
		@Override
		public int compareTo(Point o) {
			if (x == o.x)
				return y - o.y;
			return x - o.x;
		}
	}
	
	public static void main(String args[]) throws NumberFormatException, IOException{
		Scanner sc  = new Scanner();
		int N = sc.nextInt();
		TreeSet<Point> set = new TreeSet<Point>();
		
		Point[] array = new Point[N];
		for(int i = 0; i < N; i++){
			array[i] = new Point( sc.nextInt(), sc.nextInt());
			set.add(array[i]);
		}
		int count  = 0;
		for(int i = 0; i < N; i++)
			for(int j = i + 1; j < N; j++){
				Point p = array[i].add(array[j]);
				if (!p.isvalid())
					continue;
				p = p.mid();
				if (set.contains(p))
					count++;
			}
		System.out.println(count);
			
	}

}
