do calculation

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
        operator = "+"
    elif command=="subtract":
        result = number1-+number2
        operator = "-"
    output = str(result)
    print(input1+operator+input2+"="+output)
finished=False
while finished==False:
    print("Hi, I am Khamisi, your personal bot.")
    command=input("How can I help? ")
    if command=="add":
        do_calculation()
    elif command=="subtract":
        do_calculation()
    elif command=="bye":
        finished=True
    else:
        print("Sorry I don't understand this")