import time

floors_dict = {'B3': -3, 'b3': -3, 'B2': -2, 'b2': -2, 'B1': -1, 'b1': -1,  'G': 0, 'g': 0, '1': 1, '2':2 , '3':3, '4':4, '5':5, '6':6, '7':7, '8':8, '9':9, '10':10, '11':11, '12':12}
floors_list = floors_dict.keys()
floor_dict = dict((v,k) for k,v in floors_dict.items())

print("Welcome to the lift! We are asuming that you're on ground floor and starting the lift for you...")
print("Please input the floor you want to go. We have listed the options for you.\n %s"%','.join(floors_list))


current_floor_of_lift = 0 #Ground Floor
current_floor_of_user = 0 #Ground Floor
door_status = 0 #0-closed, 1-Opened

def opendoor():
	print("Opening lift door...")
	time.sleep(2)

def closedoor():
	print("Closing lift door...")
	time.sleep(2)

def move(current_floor, destination_floor):
	if current_floor < destination_floor:
		starting_floor = current_floor +1
		ending_floor = destination_floor+1
		step = 1
	elif destination_floor < current_floor:
		starting_floor = current_floor -1
		ending_floor = destination_floor-1
		step = -1
	else:
		current_floor_of_user = current_floor
		current_floor_of_lift = current_floor

	for each_floor in range(starting_floor, ending_floor, step):
		print('Moving to %s-floor'%floor_dict[each_floor])
		time.sleep(3)
		current_floor_of_user = each_floor
		current_floor_of_lift = each_floor

	return current_floor_of_user, current_floor_of_lift

while True:
	if door_status == 0:
		opendoor()
		door_status = 1
	print("The lift is on %s-floor"%floor_dict[current_floor_of_lift])
	destination_floor = input("Enter Floor here: ")
	#print(type(desination_floor))

	if destination_floor not in floors_list:
		print('Error! You have entered the wrong floor, Please Input again.')
		continue
	else:
		print('Thanks for the input! we are taking you to your destination floor.')
		closedoor()
		door_status = 0
		destination_floor = floors_dict.get(destination_floor)
		current_floor_of_user, current_floor_of_lift = move(current_floor_of_lift, destination_floor)
		print("We have reached to %s-floor"%floor_dict[current_floor_of_lift])
		if door_status == 0:
                	opendoor()
                	door_status = 1