import java.util.Scanner;

public class Main {
	
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		
		final String A = sc.next();
		final String B = sc.next();
		
		for(final char as : A.toCharArray()){
			if(!Character.isDigit(as)){ 
				System.out.println("NG"); return;
			}
		}
		for(final char bs : B.toCharArray()){
			if(!Character.isDigit(bs)){ 
				System.out.println("NG"); return;
			}
		}
		
		// - が入ってないから安心
		if(A.charAt(0) == '0' && !A.equals("0")){
			System.out.println("NG"); return;
		}
		if(B.charAt(0) == '0' && !B.equals("0")){
			System.out.println("NG"); return;
		}
		
		System.out.println("OK");
	}
}