import java.util.Scanner;
class SimpleCalculator {
    public static void main(String[] args) {
        Scanner input = new Scanner(System.in);

        System.out.print("Enter the first number: ");
        double num1 = input.nextDouble();

        System.out.print("Enter the second number: ");
        double num2 = input.nextDouble();

        System.out.println("Choose an operation:");
        System.out.println("1. Addition (+)");
        System.out.println("2. Subtraction (-)");
        System.out.println("3. Multiplication (*)");
        System.out.println("4. Division (/)");

        System.out.print("Enter the operation number: ");
        int operation = input.nextInt();

        double result;

        switch (operation) {
            case 1:
                result = num1 + num2;
                System.out.println("Result: " + result);
                break;
            case 2:
                result = num1 - num2;
                System.out.println("Result: " + result);
                break;
            case 3:
                result = num1 * num2;
                System.out.println("Result: " + result);
                break;
            case 4:
                if (num2 != 0) {
                    result = num1 / num2;
                    System.out.println("Result: " + result);
                } else {
                    System.out.println("Error: Division by zero is not allowed.");
                }
                break;
            default:
                System.out.println("Invalid operation.");
        }
    }
}