import java.util.*;

public class Main {
  public static void main(String[] args) {
    Scanner sc = new Scanner(System.in);
    String a = sc.next();
    String b = sc.next();
    String ans = "OK";
    if((a.charAt(0) == '0') && (a.length() > 1)) ans = "NG";
    if((b.charAt(0) == '0') && (b.length() > 1)) ans = "NG";
    try {
      for(int i = 0; i < a.length(); i++) {
        int d = Integer.parseInt(String.valueOf(a.charAt(i)));
      }
      for(int i = 0; i < b.length(); i++) {
        int d = Integer.parseInt(String.valueOf(b.charAt(i)));
      }
    } catch(NumberFormatException e) {
      ans = "NG";
    }
    System.out.println(ans);
  }
}