def do_calculation():
    print("Let's " + user_command + " some numbers")
    input1 = input("Number 1: ")
    input2 = input("Number 2: ")
    number1 = int(input1)
    number2 = int(input2)
    if user_command == "add" or user_command == "Add" or user_command == "ADD" or user_command == "plus" or user_command == "+":
       result = number1 + number2
    elif user_command == "subtract" or user_command == "Subtract" or user_command == "SUBTRACT"or user_command == "minus" or user_command == "-":
        result = number1 - number2
    output = str(result)
    if user_command == "add" or user_command == "Add" or user_command == "ADD" or user_command == "plus" or user_command == "+":
        print(input1 + " + " + input2 + " = " + output)
    elif user_command == "subtract" or user_command == "Subtract" or user_command == "SUBTRACT"or user_command == "minus" or user_command == "-":
        print(input1 + " - " + input2 + " = " + output)

finished = False
while finished == False:
    print("Hi, I am Marvin, your personal bot.")
    print("Let's get started.")

    # Ask user to enter their name
    users_name = input("Can you start by telling me your name? ")
    print("Welcome " + users_name + ". It's nice to meet you.")
    # Ask user to choose an operation
    user_command = input("What do you want to add, subtract, multiply, divide, find the perimeter of a rectangle, find an average, or create a shopping list? ")
    # Respond and answer question
    if user_command == "add" or user_command == "Add" or user_command == "ADD" or user_command == "plus" or user_command == "+":
       do_calculation()
    elif user_command == "subtract" or user_command == "Subtract" or user_command == "SUBTRACT"or user_command == "minus" or user_command == "-":
        do_calculation()