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.*;
public class Main {
	public static class punto implements Comparable{
		int x;
		int y;
		punto(int x,int y){
			this.x=x;
			this.y=y;
		}		
		public int compareTo(Object o) {			
			punto p2=(punto) o;
			if(this.x<p2.x)
				return -1;
			if(this.x==p2.x)
				return 0;
			if(this.x>p2.x)
				return 1;
			return 0;
		}
		
		public String toString() {
			return "punto [x=" + x + ", y=" + y + "]";
		}	
		
	}
	public static void main(String[] args) {
		Scanner sc= new Scanner(System.in);
		int n;
		while(sc.hasNext()){
		n=sc.nextInt();
		punto puntos[]= new punto[n];
		for(int i=0; i<n; i++){
			puntos[i]=new punto(sc.nextInt(),sc.nextInt());
		}		
		Arrays.sort(puntos);
		int max=0;
		int sum=2;
		
		for(int i=0; i<n-2; i++)
			while(i+sum<n){
				for(int j=i+1; j<i+sum; j++){
					if((puntos[i].x+puntos[i+sum].x)/2.0==(double)puntos[j].x)
						if((puntos[i].y+puntos[i+sum].y)/2.0==(double)puntos[j].y){
							max++;
							j=i+sum;
						}
					
				}
				sum++;
			}
		System.out.println(max);		
	}
	}
}
