def do_calculation():
    print("lets" + command + " some numbers")
    input1 = input("Number 1> ")
    input2 = input("Number 2> ")
    number1 = int(input1)
    number2 = int(input2)
    if command == "add":
        result = number1 + number2
    elif command == "subtract":
        result = number1 - number2
    output = str(result)
    if command == "add":
        result = number1 + number2
        operator = " + "
    elif command == "subtract":
        result = number1 - number2
        operator = " - "
    output = str(result)
    print(input1 + operator + input2 + " = " + output)
    
finished = False
while finished == False:
    print("Greetings!!! I am Fester, your Math bot.")
    #print("How can I help you?")
    users_name = input("What is your name? ")
    command = input("Do you want to add,subtract, average or compute MPG ?")
    if command == "add":
        do_calculation()
    elif command == "subtract":
        do_calculation()
    elif command == "average":
        how_many = input("how many numbers>")
        how_many = int(how_many)
        total = 0
        for number_count in range(how_many):
            number = input("Enter number " + str(number_count+1) + "> ")
            total = total + int(number)
        result = total / how_many
        print("the average = " + str(result))
    elif command == "MPG":
        starting_miles = input("What was your starting odometer reading ?>")
        starting_miles = int(starting_miles)
        ending_miles = input("What was your ending odometer reading ?>")
        ending_miles = int(ending_miles)
        gas_in = int(input("How many gallons did you put in ?>"))
        end_result = abs((starting_miles - ending_miles)/gas_in)
        miles_per_gallon = str(end_result)
        print("your average miles per gallon was " + miles_per_gallon)
    elif command == "bye":
        finished = True
        print("Have a great day!")
    else:
        print("Sorry " + users_name + " I can only add or subtract at this time")