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.math.BigInteger;
import java.util.*;
import java.util.Map.Entry;


public class Main {
   public static void main(String[] args) throws IOException
   {
	   (new Main()).solve();
   }
   public void Main() {
   }
   

   void solve()  throws IOException {
	  //BufferedReader in = new BufferedReader(new InputStreamReader(System.in));
	  //Scanner in = new Scanner(System.in);
	   MyReader in = new MyReader();
	  PrintWriter out = new PrintWriter(System.out);
     // Scanner in = new Scanner(new FileReader("input.txt"));
	//  PrintWriter out = new PrintWriter("output.txt");
	  
	  int n = in.nextInt();
	  int[] a = new int[n];
	  Set<Integer> s = new HashSet<Integer>();
	  
	  for (int i = 0; i < n; i++) {
		  int x = in.nextInt();
		  int y = in.nextInt();
		  int r = (x + 1000) * 2001 + y + 1000;
		  a[i] = r;
		  s.add(r);
	  }
	  
	  int count = 0;
	  for (int i = 0; i < n - 1; i++) {
		  for (int j = i + 1; j < n; j++) {
			  if ((a[i] + a[j]) % 2 == 0 && s.contains((a[i] + a[j])/2)) {
				  count++;
			  }
		  }
	  }
	  
	  out.print(count);
	  
	out.close(); 
   }     

};

class MyReader {
	private BufferedReader in;
	String[] parsed;
	int index = 0;

	public MyReader() {
		in = new BufferedReader(new InputStreamReader(System.in));
	}

	public int nextInt() throws NumberFormatException, IOException {
		if (parsed == null || parsed.length == index) {
			read();
		}
		return Integer.parseInt(parsed[index++]);
	}
	
	public long nextLong() throws NumberFormatException, IOException {
		if (parsed == null || parsed.length == index) {
			read();
		}
		return Long.parseLong(parsed[index++]);
	}
	
	public String nextString() throws IOException {
		if (parsed == null || parsed.length == index) {
			read();
		}
		return parsed[index++];
	}

	private void read() throws IOException {
		parsed = in.readLine().split(" ");
		index = 0;
	}

	public String readLine() throws IOException {
		return in.readLine();
	}
};