def get_sum(num1, num2):
    return num1 + num2


def subtract(num1, num2):
    return num1 - num2


def divide(num1, num2):
    return num1 / num2


def multiply(num1, num2):
    return num1 * num2


def get_operation():
    operator_input = raw_input("Please enter a valid sign (+,-,/-*): ")
    switcher = {
        "+": get_sum,
        "-": subtract,
        "/": divide,
        "*": multiply
    }
    # operation func returns the appropriate function or "Invalid sign" string.
    operation_func = switcher.get(operator_input, "Invalid sign")
    if operation_func == "Invalid sign":
        return get_operation()  # This is recursion meaning invoking a function from itself
    return operation_func


def get_num(input_message):
    try:
        num = float(raw_input(input_message))
    except ValueError:
        return get_num("Please Enter a valid number: ")
    return num


def calculate(operation, num1, num2):
    res = operation(num1, num2)
    # Checks if the calculated answer is an integer so it doesn't print with .0 at the end.
    if res % 1 == 0:
        return int(res)
    return float(res)


first_num = get_num("Please enter the first number: ")
second_num = get_num("Please enter the second number: ")
result = calculate(get_operation(), first_num, second_num)
print(result)