import java.util.Scanner;

public class Main {

    public static void main(String[] args) {
        Scanner input = new Scanner(System.in);
        int r = input.nextInt();
        int x = input.nextInt();
        int y = input.nextInt();
        int xx = input.nextInt();
        int yy = input.nextInt();
        double distance = Math.sqrt(Math.pow(x - xx, 2) + Math.pow(y - yy, 2));
        double res = Math.ceil(distance / (2 * r));
        System.out.println((int) res);
    }
}