GCK/While_forever_if-not-bye

def Calculate_something():
    finished=False
    print("Hello Im gigi your bot")
    print("let's get started for more practice")
    print("How can I help you?")
    while finished==False:
        print("Would you like to make an operation?")
        operation=input("Answer: type  Y or YES for YES and type N or NO for NO? >")

        if operation=="NO" or operation=="N":
            print("Bye Bye")
        elif operation=="YES" or operation=="Y":
            answer=input("Do you want to : > ( substract, add, multiply, sum or average) ?>")
            if answer=="substract" or answer=="add" or answer=="multiply":
                  input1=input("enter number 1>")
                  input2=input("Enter number2>")
                  number1=int(input1)
                  number2=int(input2)
                  print("lets "+ answer + " your numbers")
                  if answer=="substract":
                      substraction=number1-number2
                      print("Results for "+input1+ "-"+input2 + "= "+ str(substraction))
                  elif answer=="add":
                      addition=number1+number2
                      print("Result for "+input1+ "+"+input2 + "= "+str(addition))
                  elif answer=="multiply":
                      multiplication=(number1)*(number2)
                      print("Results for "+input1+ "*"+input2 + "= "+str(multiplication))
            elif answer=="sum" or answer=="average":
                how_many=int(input("How many numbers>"))
                total=0
                Average=0
                for number_count in range(how_many):
                    number=input("Enter number "+ str(number_count)+ ":>)")
                    total=total+ int(number)
                    Average=total/how_many
                if answer=="sum":
                    print("Total cost is = " + str(total))
                elif answer=="average":
                    print("The average of "+ str(total)+ " by " + str(how_many) + "= "+str(Average))
            else:
                print("Try again. I don't understand")
        elif operation=="bye":
            print("Goodbye!")
            finished=True

        else:
            print("I dont understand '"+ operation + " )'")

Calculate_something()