import java.util.*;

public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        int[] xs = new int[n];
        int[] ys = new int[n];
        for (int i = 0; i < n; i++) {
            xs[i] = sc.nextInt();
            ys[i] = sc.nextInt();
        }
        PriorityQueue<Unit> queue = new PriorityQueue<>();
        for (int i = 0; i < n - 1; i++) {
            for (int j = i + 1; j < n; j++) {
                queue.add(new Unit(i, j, xs[i] - xs[j], ys[i] - ys[j]));
            }
        }
        int count = 0;
        boolean[] used = new boolean[n];
        while (queue.size() > 0) {
            Unit u = queue.poll();
            if (used[u.left] || used[u.right]) {
                continue;
            }
            if (u.left == 0) {
                used[u.right] = true;
                count++;
            } else {
                used[u.left] = true;
                used[u.right] = true;
            }
        }
        System.out.println(count);
    }
    
    static class Unit implements Comparable<Unit> {
        int left;
        int right;
        long dist;
        
        public Unit(int left, int right, long x, long y) {
            this.left = left;
            this.right = right;
            dist = x * x + y * y;
        }
        
        public int compareTo(Unit another) {
            if (dist == another.dist) {
                return 0;
            } else if (dist < another.dist) {
                return -1;
            } else {
                return 1;
            }
        }
    }
}