a,b=input(),input()
chk=True
for i in a:
    if i not in '0123456789':
        print('NG')
        exit()
    if len(a)==1: chk=False
    if chk:
        if i=='0':
            print('NG')
            exit()
        else:
            chk=False
chk=True
for i in b:
    if i not in '0123456789':
        print('NG')
        exit()
    if len(b)==1: chk=False
    if chk:
        if i=='0':
            print('NG')
            exit()
        else:
            chk=False
print('OK')