while(1):
    print("Welcome! How many people, please?\nEnter 'quit' to end the program.")
    resp = input()
    if resp == 'quit':
        break
    else:
        number = int(resp)
        if number<1 or number >20:
            print('数字不合法')
            break
        if number<=4:
            print('Your small table is reserved!')
        elif number>4 and number<=6:
            print('Your middle table is reserved!')
        elif number>6 and number<=10:
            print('Your large table is reserved!')
        else:
            print('Sorry, there is no free table that seats over ten persons.')