i = 0
tname = ‘tom‘
tpasswd = ‘123456‘
for i in range(3):
#while i<3:
	username = (input(‘please input username:‘)).strip()
	password = input(‘please input password:‘)
	if username == ‘‘:
		i += 1
		if i != 3:
			print(‘username can not be empey. you left %d times‘ %(3-i))
		
	elif username != tname or password != tpasswd:
		i += 1
		if i != 3:
			print(‘username or password is uncorrect. you left %d times‘ %(3-i))
	elif username == tname and password == tpasswd:
		print(‘welcome %s login.‘ %username)
		break
else:
	print(‘over, try next day.‘)