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.*;
import java.util.*;
public class Main {

	public static void main(String[] args) throws IOException {
		BufferedReader in = new BufferedReader(new InputStreamReader(System.in));
		int n = Integer.parseInt(in.readLine().trim());
		Point[] points = new Point[n];
		TreeMap<Point, Integer> set = new TreeMap<>();
		TreeSet<Triple> tri = new TreeSet<>();
		for(int i = 0; i < n; i++){
			String[] arr = in.readLine().trim().split(" ");
			Point p = new Point(Integer.parseInt(arr[0]) * 2, Integer.parseInt(arr[1]) * 2);
			points[i] = p;
			set.put(p, 0);
		}

		for(int i = 0; i < n - 1; i++){
			for(int j = i + 1; j < n; j++){
				Point p = get(points[i], points[j]);
				if(set.containsKey(p)){
					tri.add(new Triple(i, j));
				}
			}
		}
		System.out.println(tri.size());
	}
	public static Point get(Point p1, Point p2){
		return new Point((p2.x + p1.x) / 2, (p2.y + p1.y) / 2);
	}

}
class Point implements Comparable<Point>{
	int x;
	int y;
	Point(int xx, int yy){
		x = xx;
		y = yy;
	}
	public int compareTo(Point p){
		if(x == p.x)
			return y - p.y;
		else
			return x - p.x;
	}
}
class Triple implements Comparable<Triple>{
	int i, j;
	public Triple(int ii, int jj){
		i = ii;
		j = jj;
	}
	public int compareTo(Triple t){
		if(i == t.i){
			if(j == t.j){
					return 0;
			}
			else
				return j - t.j;
		}
		else
			return i - t.i;
	}
}