def main():

        while True:
            try:
                num1 = float(input("Enter the first number: "))
                operator = input("Choose an operation (+, -, *, /): ")
                num2 = float(input("Enter the second number: "))
                break
            except ValueError:
                print("Invalid input. Please enter numbers and a valid operator (+, -, *, /).")
        
        try:
            if operator == "+":
                result = num1 + num2
            elif operator == "-":
                result = num1 - num2
            elif operator == "*":
                result = num1 * num2
            elif operator == "/":
                if num2 == 0:
                    result="Error"
                    raise ValueError("Division by zero is not allowed.")
                    
                result = num1 / num2
            else:
                raise ValueError("Invalid operator. Please choose one (+, -, *, /).")
                    
        except ValueError as e:
            print(e)
        
        print(f"Result: {result}")

if __name__ == "__main__":
    main()