A = input()
B = input()

num = [str(i) for i in range(10)]
ls = [A, B]

flag = 0
for i in ls:
    for j in i:
        if j not in num:
            flag = 1
if flag == 1:
    None
else:
    for i in ls:
        if len(i) == 1:
            flag = 0
        else:
            if i[0] == '0':
                flag = 1
if flag == 0:
    print('OK')
else:
    print('NG')