import java.util.*;
class A{
	static Scanner s = new Scanner(System.in);
	public static void main(String[] args){
		if(check(s.next())&&check(s.next())) {
			System.out.println("OK");
		}else {
			System.out.println("NG");
		}
	}
	static boolean check(String next) {
		if(next.equals("0"))
			return true;
		return next.matches("[1-9][0-9]+");
	}
}