a = str(input())
b = str(input())

def is_ok(s):
    if not s.isdecimal():
        return False
    if len(s) >= 2 and s[0] == '0':
        return False
    if int(s) < 0 or int(s) > 12345:
        return False
    return True

if is_ok(a) and is_ok(b):
    print('OK')
else:
    print('NG')