import java.util.*;

public class Solution {

    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        int r = scanner.nextInt();
        int x = scanner.nextInt();
        int y = scanner.nextInt();
        int x1 = scanner.nextInt();
        int y1 = scanner.nextInt();
        double length = Math.sqrt(Math.pow(x-x1, 2) + Math.pow(y - y1, 2));
        int d = 2 * r;
        if (d <= length) {
            System.out.print((int) Math.ceil(length / d));
        } else {
            System.out.print(0);
        }
    }
}