l = []
l.append(input())
l.append(input())
flag = True

for s in l:
    if len(s) == 1 and s == '0':
        pass
    elif len(s) > 1 and s[0:1] == '0':
        flag = False
    elif s.isdigit():
        pass
    else:
        flag = False
if flag:
    print('OK')
else:
    print('NG')