using System;

namespace ConsoleApp1
{
    delegate double MyFunc(double x);

    delegate double MyMethod(double f);

    class Test
    {
        public static double f1(double x)
        {
            return x;
        }

        public static double f2(double x)
        {
            return x * x;
        }

        public static double f3(double x)
        {
            return (double) Math.Sqrt(x);
        }
        static double divCut(MyFunc f, int t)
        {
            //метод деления отрезка попалам
            double a, b, e;
            a = double.Parse(Console.ReadLine());
            b = double.Parse(Console.ReadLine());
            e = double.Parse(Console.ReadLine());
            double length = b - a;
            double middle = (b - a) / 2;
            switch (t)
            {
                case 1:
                    if (f(a) == 0)
                    {

                        return a;
                    }
                    else if (f(b) == 0)
                    {
                        return b;
                    }
                    else
                    {
                        while (length / 2 > e)
                        {
                            length /= 2;
                            if (Math.Sign(f(a)) == Math.Sign(f(a + length)))
                            {
                                a += length;
                            }
                            else
                            {
                                b -= length;
                            }
                        }

                        return a + length;
                    }
                case 2:
                    if (f(a) == 0)
                    {
                        return a;
                    }
                    else if (f(b) == 0)
                    {
                        return b;
                    }
                    else
                    {
                        while (length / 2 > e)
                        {
                            length /= 2;
                            if (Math.Sign(f(a)) == Math.Sign(f(a + length)))
                            {
                                a += length;
                            }
                            else
                            {
                                b -= length;
                            }
                        }

                        return a + length;
                    }
                case 3:
                    if (f(a) == 0)
                    {
                        return a;
                    }
                    else if (f(b) == 0)
                    {
                        return b;
                    }
                    else
                    {
                        while (length / 2 > e)
                        {
                            length /= 2;
                            if (Math.Sign(f(a)) == Math.Sign(f(a + length)))
                            {
                                a += length;
                            }
                            else
                            {
                                b -= length;
                            }
                        }

                        return a + length;
                    }
            }

            return a + length;
        }
        static double hord()
        {
            return 1;
        }
        static double kas()
        {
            return 1;
        }
        static void Main()
        {
            MyFunc f = new MyFunc(f1);
            int a;
            Console.WriteLine("1 - x, 2 - x^2, 3 - sqrt(x)");
            a = int.Parse(Console.ReadLine());
            switch (a)
            {
                case 1:
                    MyMethod g = new MyMethod(f1);
                    break;
                case 2:
                    g = new MyMethod(f2);
                    break;
                case 3:
                    g = new MyMethod(f3);
                    break;
            }

            double x = 4;
            Console.WriteLine("f({0}) = {1}", x, g(x));
        }
}
}