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.InputStreamReader;
import java.io.IOException;
import java.io.PrintWriter;
import java.util.Comparator;
import java.util.HashMap;
import java.util.StringTokenizer;

public class B181{
	public static void main(String[] args){
		InputReader in = new InputReader();
		PrintWriter out = new PrintWriter(System.out);
		final long start = System.currentTimeMillis();
		new Task1().solve(in, out);
		final long duration = System.currentTimeMillis()-start;
		out.close();
	}

	static class Task1{
		static class Point{
			Integer hash;
			Double x, y;
			public Point(double x, double y){
				this.x=x; this.y=y;
			}

			public int hashCode(){
				if(hash!=null) return hash;
				return hash=(int)((x*2000)+y);
			}

			public boolean equals(java.lang.Object o){
				Point p = (Point)o;
				return x.equals(p.x) && y.equals(p.y);
			}
		}

		class BY_X implements Comparator<Point>{
			public int compare(Point X, Point Y){
				if(X.x>Y.x) return 1;
				else if(X.x<Y.x) return -1;
				else return X.y.compareTo(Y.y);
			}
		}

		public void solve(InputReader in, PrintWriter out){
			int n=in.nextInt();
			Point[] p = new Point[n];
			HashMap<Point, Boolean> map = new HashMap<Point, Boolean>();

			for(int i=0; i<n; i++){
				int x=in.nextInt(), y=in.nextInt();
				p[i] = new Point(x, y);
				map.put(p[i], true);
			}
			//java.util.Arrays.sort(p, new BY_X());

			int ans=0;
			for(int i=0; i<n; i++){
				for(int j=i+1; j<n; j++){
					Point temp = new Point((p[i].x+p[j].x)/2, (p[i].y+p[j].y)/2);
					if(map.containsKey(temp)) ans++;
				}
			}
			out.println(ans);
		}
	}

	static class InputReader{
		private BufferedReader reader;
		private StringTokenizer tokenizer;
		
		public InputReader(){
			reader = new BufferedReader(new InputStreamReader(System.in));
			tokenizer = null;
		}

		public String next(){
			while(tokenizer==null || !tokenizer.hasMoreTokens()){
				try{
					tokenizer = new StringTokenizer(reader.readLine());
				} catch (IOException e){
					throw new RuntimeException(e);
				}
			}
			return tokenizer.nextToken();
		}

		public int nextInt(){
			return (int)Integer.parseInt(next());
		}

		public long nextLong(){
			return (long)Long.parseLong(next());
		}

		public double nextDouble(){
			return (double)Double.parseDouble(next());
		}

		public String nextLine(){
			String s = null;
			try{
				s = reader.readLine();
			} catch(Exception e){
				throw new RuntimeException(e);
			}
			return s;
		}
	}
}