#3OperationsWithFourDigitNum

static void Main()
        {
            Console.WriteLine("Enter a random four digit number: ");
            int number = int.Parse(Console.ReadLine());
            //detach the four digits; convert them into whole numbers
            int a = number / 1000;
            int b = (number - a * 1000) / 100;
            int c = (number - (a * 1000 + b * 100)) / 10;
            int d = (number - (a * 1000 + b * 100 + c * 10));
            //calculations
            int sum = a + b + c + d;
            //console output
            Console.WriteLine("Sum of digits: " + sum);
            Console.WriteLine("Reversed: {0}{1}{2}{3}", d, c, b, a);
            Console.WriteLine("Last digit in front: {0}{1}{2}{3}", d, a, b, c);
            Console.WriteLine("Second and third digits exchanged: {0}{1}{2}{3}", a, c, b, d);
        }