# functions go here

def yes_no(question):

    while True:
        response = input(question).lower()

        if response == "yes" or response == "y":
            return "yes"

        elif response == "no" or response == "n":
            return "no"

        else:
            print("Please answer yes or no")

# main routine starts here

# set maximum number of tickets below
MAX_TICKETS = 3
tickets_sold = 0

# instructions
want_instructions = yes_no("Do you want to read the instructions? ").lower()

if want_instructions == "yes":
    print("xyz")

# loop to sell tickets
tickets_sold = 0
while tickets_sold < MAX_TICKETS:
    name = input("Please enter your name or 'xxx' to quit: ")

    if name == 'xxx':
        break

    tickets_sold += 1

# Output number of tickets sold
if tickets_sold == MAX_TICKETS:
    print("All tickets sold")
else:
    print("You have sold {} ticket/s. There is {} ticket/s "
    "remaining".format(tickets_sold, MAX_TICKETS - tickets_sold))