package yukicoder;

import java.util.Scanner;

public class Q446 {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);

		boolean correct = true;
		for (int t = 0; t < 2; ++t) {
			String s = sc.next();
			boolean ok = false;
			for (int i = 0; i <= 12345; ++i) {
				if (String.valueOf(i).equals(s)) {
					ok = true;
				}
			}
			correct &= ok;
		}

		if (correct) {
			System.out.println("OK");
		} else {
			System.out.println("NG");
		}

		sc.close();

	}
}