import java.util.Scanner;
public class Pins {
	public static void main(String [] args) {
		Scanner scan = new Scanner(System.in);
		long r = scan.nextInt(), x = scan.nextInt(), y = scan.nextInt(), x1 = scan.nextInt(), y1 = scan.nextInt();
		System.out.println((int)(Math.ceil(Math.sqrt((x1-x)*(x1-x)+(y1-y)*(y1-y))/(2*r))));
	}
}