#include <stdio.h>
#include <string.h>
int main(void){
    char A[6];
    char B[6];
    int i;

    for(int count = 0; count < 2; count++){
        scanf("%s",A);
        if(strlen(A) > 1){
            // 012 -> NG
            // A > 12345 -> NG 
            if(A[0] == 48){
                printf("NG\n");
                return 0;
            }else if(strlen(A) == 5 && strcmp(A,"12345") > 0){
                printf("NG\n");
                return 0;
            }else{
                for(i = 0; A[i] != 0; i++){
                    //  out of 0 ~ 9 -> NG
                    if(A[i] < 48 || A[i] > 57){
                        printf("NG\n");
                        return 0;
                    }
                }
            }
        }else{
            //  out of 0 ~ 9 -> NG
            if(A[0] < 48 || A[0] > 57){
                printf("NG\n");
                return 0;
            }
        }
    }
    
    printf("OK\n");
    return 0;
}