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.HashSet;
import java.util.Set;

public class B {

	public B () throws IOException {
		int N = sc.nextInt();
		int [][] P = new int [N][2];
		for (int [] p : P) {
			p[0] = sc.nextInt() + 1000;
			p[1] = sc.nextInt() + 1000;
		}
		solve(N, P);
	}
	
	public void solve (int N, int [][] P) {
		Set<Integer> S = new HashSet<Integer>();
		for (int [] p : P)
			S.add(10000*p[0] + p[1]);
		
		int res = 0;
		for (int n = 0; n < N; ++n)
			for (int m = n+1; m < N; ++m) {
				int xx = P[n][0] + P[m][0], yy = P[n][1] + P[m][1];
				if (xx % 2 == 0 && yy % 2 == 0) {
					int x = xx/2, y = yy/2;
					if (S.contains(10000*x+y))
						++res;
				}
				
			}
		exit (res);
	}
	
	////////////////////////////////////////////////////////////////////////////////////
	
	static MyScanner sc;
	static long t;
	
	static void print (Object o) {
		System.out.println(o);
	}
	
	static void exit (Object o) {
		print(o);
		//print2((millis() - t) / 1000.0);
		System.exit(0);
	}
	
	static void run () throws IOException {
		sc = new MyScanner ();
		new B();
	}
	
	public static void main(String[] args) throws IOException {
		run();
	}
	
	static long millis() {
		return System.currentTimeMillis();
	}
	
	static void start() {
		t = millis();
	}
	
	static class MyScanner {
		String next() throws IOException {
			newLine();
			return line[index++];
		}
		
		char [] nextChars() throws IOException {
			return next().toCharArray();
		}
		
		double nextDouble() throws IOException {
			return Double.parseDouble(next());
		}
		
		int nextInt() throws IOException {
			return Integer.parseInt(next());
		}
		
		long nextLong() throws IOException {
			return Long.parseLong(next());
		}
		
		String nextLine() throws IOException {
			line = null;
			return r.readLine();
		}
		
		
		String [] nextStrings() throws IOException {
			line = null;
			return r.readLine().split(" ");
		}
		
		int [] nextInts() throws IOException {
			String [] L = nextStrings();
			int [] res = new int [L.length];
			for (int i = 0; i < L.length; ++i)
				res[i] = Integer.parseInt(L[i]);
			return res;
		}
		
		
		long [] nextLongs() throws IOException {
			String [] L = nextStrings();
			long [] res = new long [L.length];
			for (int i = 0; i < L.length; ++i)
				res[i] = Long.parseLong(L[i]);
			return res;
		}

		boolean eol() {
			return index == line.length;
		}

		//////////////////////////////////////////////
		
		private final BufferedReader r;

		MyScanner () throws IOException {
			this(new BufferedReader(new InputStreamReader(System.in)));
		}
		
		MyScanner(BufferedReader r) throws IOException { 
			this.r = r;
		}
		
		private String [] line;
		private int index;

		private void newLine() throws IOException {
			if (line == null || index == line.length) {
				line = r.readLine().split(" ");
				index = 0;
			}
		}		
	}	
}
