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.util.*;
import java.math.*;
import java.awt.Point;
import java.io.*;
public class Main
	{
	public static void main(String args[])	throws IOException
		{
		//BufferedReader c=new BufferedReader(new InputStreamReader(System.in));
		Scanner c=new Scanner(System.in);
		
		int N=c.nextInt();
		node A[]=new node[N];
		TreeSet<node> T=new TreeSet<node>();
		int ans=0;
		for(int i=0;i<N;i++) 
			{
			int a=c.nextInt();
			int b=c.nextInt();
			A[i]=new node(a,b);
			T.add(new node(a,b));
			}
		for(int i=0;i<N;i++) 
			{
			for(int j=i+1;j<N;j++) 
				{
			
				int sumX=A[i].x+A[j].x;
				int sumY=A[i].y+A[j].y;
				if(sumX%2!=0||sumY%2!=0)
					continue;
				else
					{
					int midX=sumX/2;
					int midY=sumY/2;
					if(T.contains(new node(midX,midY)))
						ans++;
					}
				}
			}
		System.out.println(ans);
		}
	}
class node implements Comparable<node>
	{
	int x;
	int y;
	public node(int x,int y)
		{
		this.x=x;
		this.y=y;
		}
	public int compareTo(node o)
		{
		if(this.x<o.x)
			return -1;
		else if(this.x==o.x&&this.y<o.y)
			return -1;
		else if(this.x==o.x&&this.y==o.y)
			return 0;
		return 1;
		}
	}
//must declare new classes here