import java.util.Scanner;

public class CR287A {
	public static void main(String[] args) {

		Scanner s = new Scanner(System.in);

		long r = s.nextLong();

		int x = s.nextInt();
		int y = s.nextInt();
		int x1 = s.nextInt();
		int y1 = s.nextInt();

		System.out.println((int) (Math.ceil(Math.sqrt((x1 - x) * (x1 - x) + (y1 - y) * (y1 - y)) / (2 * r))));

	}
}
