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.io.PrintWriter;
import java.util.SortedSet;
import java.util.StringTokenizer;
import java.util.TreeSet;

public class Main {

	static PrintWriter out = new PrintWriter(System.out);
	static FastReader input = new FastReader();
	static int [][] point;
	static int n;

	

	public static void main(String args[]) throws IOException {
		 n = input.nextInt();
		point = new int [n][2];
		int sum = 0 ; 
		SortedSet [] z   = new SortedSet[2001];
		
		for (int i= 0 ; i < 2001; i++) {
			z[i] = new TreeSet();
		}
		
		for (int i = 0 ; i< n ; i++) {
			point[i][0] = input.nextInt();
			point[i][1] = input.nextInt();
			z[point[i][0]+1000].add(point[i][1]);
		}
		

		
		for (int i = 0 ; i < n ; i++) {
			for (int j = i+1 ; j < n ; j++) {
				
				float keyX = (float) ((point[i][0]+point[j][0])/2.0);
				float keyY = (float) ((point[i][1]+point[j][1])/2.0);
				
				if (Math.abs(keyX-Math.round(keyX))<0.0000001&&
					Math.abs(keyY-Math.round(keyY))<0.0000001) {
					if (z[Math.round(keyX)+1000].contains(Math.round(keyY))) {
						sum++;
					}
				} 
				
				
			}
		}
		
		out.print(sum);

		
		out.flush();
	}

	static class FastReader {
		BufferedReader br;
		StringTokenizer st;

		public FastReader() {
			br = new BufferedReader(new InputStreamReader(System.in));
		}

		String next() throws IOException {
			while (st == null || !st.hasMoreElements()) {
				st = new StringTokenizer(br.readLine());
			}
			return st.nextToken();
		}

		int nextInt() throws NumberFormatException, IOException {
			return Integer.parseInt(next());
		}

		long nextLong() throws NumberFormatException, IOException {
			return Long.parseLong(next());
		}

		double nextDouble() throws NumberFormatException, IOException {
			return Double.parseDouble(next());
		}

		String nextLine() throws IOException {
			String str = "";
			str = br.readLine();
			return str;
		}
	}

}