u=lambda:map(lambda t:ord(t)-0x30,raw_input().strip());v=lambda x:int(''.join(map(lambda t:chr(t+0x30),x)));a=u();b=u();print(all([0<=x<=9 for x in a+b])&(not(len(a)>1 and a[0]!=0)and(len(b)>1 and b[0]!=0))and(v(a)<12346 and v(b)<12346))and'OK'or'NG'