using System;

public class Program

{

    public static void Main()

    {

        t1();

        t2();

        t3();

    }

    public static void t3(){

        Console.WriteLine("Task 3");

        double x = 0.5, a = 4.3, y = 2.6, d = 0.3, v = 0;

        Console.Write("Input n - ");

        int n = Convert.ToInt32(Console.ReadLine());

        switch(n){

            case 2:

                Console.WriteLine("Case {0}", n);

                v = 1.5 * x + 9 * Math.Pow(x, 2) + 1.25;

                break;

            case 5:

                Console.WriteLine("Case {0}", n);

                v = d + a * Math.Sin(x);

                break;

            case 1:

                Console.WriteLine("Case {0}", n);

                v = (a - x + y / d);

                break;

            default:

                v = 0;

                Console.WriteLine("Default case with number {0}", n);

                break;

        }

        Console.WriteLine("Output v - {0}", v);

    }

    private static void t2(){

        Console.WriteLine("Task 2");

        Console.Write("Input n - ");

        double n = Convert.ToDouble(Console.ReadLine());

        Console.Write("Input x - ");

        double x = Convert.ToDouble(Console.ReadLine());

        double sumOfElements = 0;

        for (int i = 1; i <= n; i++){

            sumOfElements += (x + Math.Cos(i * x)) / Math.Pow(2, i);

        }

        Console.WriteLine("Output sumOfElements - {0}", sumOfElements);

    }

    private static void t1(){

        Console.WriteLine("Task 1");

        Console.Write("Input x - ");

        double x = Convert.ToDouble(Console.ReadLine());

        if (x >= 0){

            Console.WriteLine("x >= 0");

            x = Math.Sqrt(Math.Pow(x, 3) + 5);

        } 

        else if (-3 < x && x < 0){

            Console.WriteLine("-3 < x < 0");

            x = 3 * Math.Pow(x, 4) + 9;

        }

        Console.WriteLine("Output x - {0}", x);

    }

}