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 test2
{

	public static void main(String[] args) throws Exception
	{
		new test2().run();
	}

	PrintWriter out = null;

	HashSet<String> hs = new HashSet<String>();
	int n;
	int[] x = null;
	int[] y = null;

	void run() throws Exception
	{
		Scanner in = new Scanner(System.in);
		out = new PrintWriter(System.out);

		n = in.nextInt();
		x = new int[n];
		y = new int[n];
		for (int i = 0; i < n; i++)
		{
			x[i] = in.nextInt();
			y[i] = in.nextInt();

			String key = x[i] + ":" + y[i];
			hs.add(key);
		}

		int count = 0;

		for (int i = 0; i < n; i++)
			for (int j = i + 1; j < n; j++)
			{
				if ((x[j] - x[i]) % 2 != 0 || (y[j] - y[i]) % 2 != 0)
					continue;

				int a = Math.min(x[i], x[j]) + Math.abs((x[i] - x[j]) / 2);
				int b = Math.min(y[i], y[j]) + Math.abs((y[i] - y[j]) / 2);

				String key = a + ":" + b;
				if (hs.contains(key))
					count++;
			}

		out.println(count);
		out.close();
	}
}
