a = input()
b = input()

l = []
for i in a:
    if i.isdigit() == False:
        l.append(0)

for i in b:
    if i.isdigit() == False:
        l.append(0)
        
if 0 in l:
    print('NG')
else:
    if len(str(a)) != len(str(int(a))) or len(str(b)) != len(str(int(b))):
        print('NG')
    else:
        print('OK')