import bisect
import copy
import decimal
import fractions
import heapq
import itertools
import math
import random
import sys
import time
from collections import Counter,deque,defaultdict
from functools import lru_cache,reduce
from heapq import heappush,heappop,heapify,heappushpop,_heappop_max,_heapify_max
def _heappush_max(heap,item):
    heap.append(item)
    heapq._siftdown_max(heap, 0, len(heap)-1)
def _heappushpop_max(heap, item):
    if heap and item < heap[0]:
        item, heap[0] = heap[0], item
        heapq._siftup_max(heap, 0)
    return item
from math import gcd as GCD
read=sys.stdin.read
readline=sys.stdin.readline
readlines=sys.stdin.readlines
write=sys.stdout.write

ans="OK"
A=readline().rstrip()
B=readline().rstrip()
num=[str(i) for i in range(10)]
for a in A:
    if not a in num:
        ans="NG"
for b in B:
    if not b in num:
        ans="NG"
if len(A)>=2 and A[0]=="0":
    ans="NG"
if len(B)>=2 and B[0]=="0":
    ans="NG"
if ans=="OK":
    if not 0<=int(A)<=12345 or not 0<=int(B)<=12345:
        ans="NG"
print(ans)