def num(x): if x=="1": return 1 elif x=="2": return 1 elif x=="3": return 1 elif x=="4": return 1 elif x=="5": return 1 elif x=="6": return 1 elif x=="7": return 1 elif x=="8": return 1 elif x=="9": return 1 else: return 0 def nuli (l): n=1 i=0 while n==1 and i < len(l): if num(l[i])==0: n=0 i+=1 if len(l)>1 and l[0]==0: n=0 return n A=list(input()) B=list(input()) if nuli (A)==0 or nuli(B)==0: print ("NG") else: print ("OK")