i=input
a=i()
b=i()
for i in a:
	if not i.isdigit(): print('NG'); exit()
for i in b:
	if not i.isdigit(): print('NG'); exit()
if int(a) > 12345 or int(b) > 12345:
	print('NG')
elif (int(a) != 0 and a[0] == '0') or (int(b) != 0 and b[0] == '0'):
	print('NG')
elif (int(a) == 0 and len(a) > 1) or (int(b) == 0 and len(b) > 1):
	print('NG')
else:
	print('OK')