import java.util.Scanner;

public class Main{

    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        int r = in.nextInt();
        long dx = in.nextInt();
        long dy = in.nextInt();
        dx -= in.nextInt();
        dy -= in.nextInt();
        
        int dist = (int) Math.ceil(Math.sqrt(dx * dx + dy * dy) / (2 * r));
        System.out.println(dist);

    }

}