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.awt.Point;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.util.HashSet;
import java.util.Set;
import java.util.StringTokenizer;

public class B181 {
	static String next() {
		if (st == null || !st.hasMoreTokens())
			nextLine();
		return st.nextToken();
	}

	static int nextInt() {
		return Integer.parseInt(next());
	}

	static void nextLine() {
		try {
			st = new StringTokenizer(f.readLine());
		} catch (Exception e) {
			e.printStackTrace();
		}
	}

	static StringTokenizer st;
	static PrintWriter out;
	static BufferedReader f;

	public static void main(String[] args) throws IOException {
		f = new BufferedReader(new InputStreamReader(System.in));
		out = new PrintWriter(System.out);
		int n = nextInt();
		Point[] points = new Point[n];
		Set<Point> hs = new HashSet<Point>();
		for (int i = 0; i < n; i++) {
			hs.add(points[i] = new Point(nextInt(), nextInt()));
		}
		long trips = 0;
		for (int i = 0; i < n; i++) {
			for (int j = i + 1; j < n; j++) {
				Point mdpt = mdpt(points[i], points[j]);
				if (mdpt != null && hs.contains(mdpt))
					trips++;
			}
		}
		out.println(trips);
		out.close();
		// System.exit(0);
	}

	static Point mdpt(Point a, Point b) {
		int xs = a.x + b.x, ys = a.y + b.y;
		if (xs % 2 == 0 && ys % 2 == 0)
			return new Point(xs / 2, ys / 2);
		else
			return null;
	}
}