import java.util.Scanner;

public class Main {
	private static int bingdu(String cur, int n) {
		if (cur.length() > 10 || Integer.parseInt(cur) > n) {
			return 0;
		} else {
			return 1 + bingdu(cur + "0", n) + bingdu(cur + "1", n);
		}
	}

	public static void main(String[] args) {
		Scanner scanner = new Scanner(System.in);
		while (scanner.hasNextInt()) {
			int n = scanner.nextInt();
			System.out.println(bingdu("1", n));
		}
		scanner.close();
	}
}