class ReturnTest
{
    static double CalculateArea(int r)
    {
        double area = r * r * Math.PI;
        return area;
    }

    static void Main()
    {
        int radius = 5;
        double result = CalculateArea(radius);
        Console.WriteLine("The area is {0:0.00}", result);

        // Keep the console open in debug mode.
        Console.WriteLine("Press any key to exit.");
        Console.ReadKey();
    }
}
// Output: The area is 78.54