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 m,n;
	
	void execute() throws IOException
	{
		totalCases = 1;
		for(testNum = 1; testNum <= totalCases; testNum++)
		{
			input();
			solve();
		}
	}

	void solve()
	{
		int count=0;
		for(int i = 0 ;i<n;i++)
			for(int j = i+1;j<n;j++)
			{
				if((g[i][0]+g[j][0])%2!=0)
					continue;
				if((g[i][1]+g[j][1])%2!=0)
					continue;
			
				int x = (g[i][0]+g[j][0])/2;
				int y = (g[i][1]+g[j][1])/2;
				if(p.containsKey(x))
				{
					HashSet<Integer> h = p.get(x);
					if(h.contains(y))
					{
						//debug(x,y);
						count++;
					}
						
				}
			}
		System.out.println(count);
	}
	
	void printarr(int [] a,int b)
	{
		for(int i = 0;i<=b;i++)
		{
			if(i==0)
				System.out.print(a[i]);
			else
				System.out.print(" "+a[i]);
		}
		System.out.println();
	}
	int[][] g ;
	HashMap<Integer,HashSet<Integer>> p;
	boolean input() throws IOException
	{
		p = new HashMap<Integer,HashSet<Integer>>();
		n = ni();
		g= new int[n][2];
		for(int i = 0 ;i<n;i++)
		{
			int x = ni();
			int y = ni();
			g[i][0]=x;
			g[i][1]=y;
			if(p.containsKey(x))
			{
				HashSet<Integer> temp = p.get(x);
				temp.add(y);
				p.put(x,temp);
			}
			else
			{
				HashSet<Integer> h = new HashSet<Integer>();
				h.add(y);
				p.put(x,h);
			}
		}
		return true;
	}
}