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.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.StringTokenizer;
import java.util.TreeSet;

public class NumberOfTriplets {
	
	static class P implements Comparable<P> {
		int x, y;
		
		P(int x, int y) {
			this.x = x;
			this.y = y;
		}

		@Override
		public int compareTo(NumberOfTriplets.P o) {
			
			if (this.x > o.x) {
				return 1;
			} else if (this.x < o.x) {
				return -1;
			} else if (this.x == o.x) {
				if (this.y > o.y) {
					return 1;
				} else if (this.y < o.y) {
					return -1;
				}
			}
			
			return 0;
		}
	}
	
	public static void main (String[] args) throws IOException {
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		StringTokenizer st = new StringTokenizer(br.readLine());
		
		int n = Integer.parseInt(st.nextToken());
		P[] pa = new P[n];
		TreeSet<P> ps = new TreeSet<P>();
		
		
		for (int i = 0; i < n; i++) {
			st = new StringTokenizer(br.readLine());
			pa[i] = new P(Integer.parseInt(st.nextToken()), Integer.parseInt(st.nextToken()));
			ps.add(pa[i]);
		}
		
		br.close();
		
		
		int count = 0;
		
		for (int i = 0; i < n - 1; i++) {
			for (int j = i + 1; j < n; j++) {
				P cm = mp(pa[i], pa[j]);
				
				if (cm == null) {
					continue;
				} else {
					
					if (ps.contains(cm)) {
						count++;
					}
					
				}
			}
		}
		
		System.out.println(count);
	}
	
	static P mp(P p1, P p2) {
		P m = null;
		
		if ((p1.x + p2.x) % 2 == 0) {
			
			if ((p1.y + p2.y) % 2 == 0) {
				
				m  = new P((p1.x + p2.x) / 2, (p1.y + p2.y) /2);
				
			}
			
		}
		
		
		return m;
	}
}
