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.util.*;
import java.math.*;
import java.io.*;
public class Main {
    public static StringTokenizer st;
    public static BufferedReader scan;
    public static PrintWriter out;
    public class Pair {
        public int x,  y;
        public Pair(int x, int y){
            this.x = x;
            this.y = y;
        }
    }
    public static void main(String[] args) throws  IOException{
        scan = new BufferedReader(new InputStreamReader(System.in));
        out = new PrintWriter(new BufferedWriter(new OutputStreamWriter(System.out)));
        int n = nextInt();
        double[] x = new double[n];
        double[] y = new double[n];
        Map <Double, Boolean>mx = new HashMap();
        Map <Double, Boolean>my = new HashMap();
        for(int i = 0; i < n; i++){
            x[i] = nextDouble(); y[i] = nextDouble();
            mx.put(x[i], true); my.put(y[i], true);
        }
        int ans = 0;
        for(int i = 0; i < n; i++){
            for(int j = i + 1; j < n && i != j; j++){
                  double x1 = (x[i] + x[j]) / 2.0;
                 double y1 = (y[i] + y[j]) / 2.0;
                if(mx.containsKey(x1) && my.containsKey(y1))ans++;
            }
        }
        out.println(ans);
        scan.close();
        out.close();
    }
    public static BigDecimal nextBigDecimal() throws  IOException {
        return new BigDecimal(next());
    }
    public static BigInteger nextBigInteger() throws  IOException {
        return new BigInteger(next());
    }
    public static long nextLong() throws  IOException {
        return Long.parseLong(next());
    }
    public static double nextDouble() throws  IOException {
        return Double.parseDouble(next());
    }
    public static int nextInt() throws  IOException {
        return Integer.parseInt(next());
    }
    public static String next() throws IOException {
        while(st == null || !st.hasMoreTokens()){
            st = new StringTokenizer(scan.readLine());
        }
        return st.nextToken();
    }
}