import java.io.IOException;
import java.util.Scanner;

public class Main{
	static int r, x1, x2, y1, y2;
	static double d;
	
	public static void main(String[] args) throws IOException {
		Scanner in = new Scanner(System.in);
		
		r = in.nextInt();
		x1 = in.nextInt();
		y1 = in.nextInt();
		x2 = in.nextInt();
		y2 = in.nextInt();
		
		d = Math.sqrt(Math.pow(x2 - x1, 2) + Math.pow(y2 - y1, 2));
		
		System.out.println((int) Math.ceil(d / (2.0 * r)));
		
		in.close();
	}
}
