a = input()
b = input()
if a.isdigit() and b.isdigit():
    flag = True
    if len(a) >= 2 and a[0] == "0":
        flag = False
    if len(b) >= 2 and b[0] == "0":
        flag = False
    if flag:
        print("OK")
    else:
        print("NG")
else:
    print("NG")