import java.util.Scanner;

/**
 * Created by nullzine on 2017/01/13.
 */
public class Main {

    public static void main(String[] args){
        System.out.println(new Main().run());
    }

    private String run(){
        Scanner sc = new Scanner(System.in);
        int aa,bb;
        String a,b;
        a = sc.nextLine();
        b = sc.nextLine();
        if(zeroValidation(a)||zeroValidation(b)){
            return "NG";
        }
        try{
            aa=Integer.parseInt(a);
            bb=Integer.parseInt(b);
        }catch(NumberFormatException e){
            return "NG";
        }
        return "OK";
    }

    private boolean zeroValidation(String str){
        return !str.equals("0")&&str.charAt(0)=='0';
    }

}