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.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.List;
import java.util.StringTokenizer;
import java.util.TreeSet;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

public class Main {

	/**
	 * @param args
	 * @throws IOException
	 * @throws NumberFormatException
	 */
	public static void main(String[] args) throws NumberFormatException, IOException {
		new Main().run();
	}

	private StringTokenizer input;
	private BufferedReader reader;
	
	private static class Point implements Comparable<Point> {
		int x;
		int y;
		
		Point(int x, int y) {
			this.x = x;
			this.y = y;
		}
		
		@Override
		public int hashCode() {
			return makeHash(x, y);
		}
		
		@Override
		public boolean equals(Object obj) {
			if (!(obj instanceof Point)) {
				return false;
			}
			
			Point other = (Point) obj;
			return other.x == x && other.y == y;
		}

		@Override
		public int compareTo(Point o) {
			return this.hashCode() - o.hashCode();
		}
		
		@Override
		public String toString() {
			return String.valueOf(hashCode());
		}
	}
	
	private void run() throws NumberFormatException, IOException {
		openInput(null);

		int n = nextInt();
		Collection<Point> _hashes = new TreeSet<>();
		for (int i = 0; i < n; i++) {
			_hashes.add(new Point(nextInt(), nextInt()));
		}
		List<Point> hashes = new ArrayList<>();
		hashes.addAll(_hashes);
		_hashes = null;
		
		int count = 0;
		Point p = new Point(0, 0);
		for (int i = 0; i < n - 2; i++) {
			for (int j = i + 2; j < n; j++) {
				Point p1 = hashes.get(i);
				Point p2 = hashes.get(j);
				int h = p1.x + p2.x;
				if (h % 2 != 0) {
					continue;
				}
				p.x = h / 2;
				h = p1.y + p2.y;
				if (h % 2 != 0) {
					continue;
				}
				p.y = h / 2;
				if (Collections.binarySearch(hashes, p) > 0) {
					count++;
				}
			}
		}
		System.out.println(count);
		
		closeInput();
	}
	

	private static int makeHash(int x, int y) {
		return 1000000000 + x*100000 + 10000 + y;
	}


	private void openInput(String fileName) {
		reader = new BufferedReader(new InputStreamReader(System.in));
	}
	
	private void closeInput() {
		try {
			reader.close();
		} catch (IOException e) {
			e.printStackTrace();
		}
	}
	
	private String next() throws IOException {
		while (input == null || !input.hasMoreTokens()) {
			input = new StringTokenizer(reader.readLine());
		}
		return input.nextToken();
	}
	
	@SuppressWarnings("unused")
	private long nextLong() throws NumberFormatException, IOException {
		return Long.parseLong(next());
	}
	
	@SuppressWarnings("unused")
	private int nextInt() throws NumberFormatException, IOException {
		return Integer.parseInt(next());
	}
	
	@SuppressWarnings("unused")
	private double nextDouble() throws NumberFormatException, IOException {
		return Double.parseDouble(next());
	}

}
