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.*;
import java.math.*;

public class Main
{
	BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
	StringTokenizer tokenizer=null;
	
	public static void main(String[] args) throws IOException
	{
		new Main().execute();
	}
	
	void debug(Object...os)
	{
		System.out.println(Arrays.deepToString(os));
	}
	
	int ni() throws IOException
	{
		return Integer.parseInt(ns());
	}
	
	long nl() throws IOException 
	{
		return Long.parseLong(ns());
	}
	
	double nd() throws IOException 
	{
		return Double.parseDouble(ns());
	}
		
	String ns() throws IOException 
	{
		while (tokenizer == null || !tokenizer.hasMoreTokens()) 
			tokenizer = new StringTokenizer(br.readLine());
		return tokenizer.nextToken();
	}
	
	String nline() throws IOException
	{
		tokenizer=null;
		return br.readLine();
	}
		
	

	//Main Code starts Here
	int totalCases, testNum;
	//int MAXN = 2010;
	int n;	
	int x[];
	int y[];
	//boolean arr[];

	void execute() throws IOException
	{
		totalCases = 1;
		for(testNum = 1; testNum <= totalCases; testNum++)
		{
			if(!input())
				break;
			solve();
		}
	}
	HashSet<Integer> hs;
	void solve() throws IOException
	{
		int count = 0;
		for(int i = 0;i<n;i++)
		{
			for(int j = 0;j<n;j++)
			{
				if(i!=j)
				{
					int dx = (x[i]+x[j])/2;
					int dy = (y[i]+y[j])/2;
					if(dx*2 == (x[i]+x[j]) && dy*2 == (y[i]+y[j]))
					{
						int a = dx*10000 + dy;//String.valueOf(dx)+","+String.valueOf(dy);
						if(hs.contains(a))
							count++;							
					}
				}
			}
		}
		System.out.println(count/2);
	}

	boolean input() throws IOException
	{
		n = ni();
		x = new int[n];
		y = new int[n];
		hs = new HashSet<Integer>();
		for(int i = 0;i<n;i++)
		{
			x[i] = ni();
			y[i] = ni();
			int a = x[i]*10000 + y[i];			
			//String a = String.valueOf(x[i])+","+String.valueOf(y[i]);
			hs.add(a);
		}
		return true;
	}


}


