using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace ConsoleApplication16
{
    class Program
    {
        static void Main(string[] args)
        {
            double tgx = 0;
            Console.WriteLine("Введите x");
            string str = Console.ReadLine();
            int X = int.Parse(str);
            if Tg(X,ref double tgx)
            Console.WriteLine(tgx);
            else Console.WriteLine("ошибка");
        }

        public static double BernulliNumbe(int n)
        {
            if (n == 0)
                return 1;
            if (n % 2 == 1)
                return 0;
            double sum = 0;
            for (int k = 1; k < n + 1; k++)
            {

                sum += (Factorial(n + 1) * BernulliNumbe(n - k)) / (Factorial(k + 1) * Factorial(n - k));


            }
            return (-1.0 / (n + 1)) * sum;


        }
        public static double stepen(double d, int nn)
        {
            double sum1 = 1.0;
            for (int k = 0; k <= nn; k++)
            {


                sum1 = sum1 * d;



            }
            return sum1;
        }

        public static bool Tg(int x, ref double tgx)
     {
         if (x > (-(Math.PI) / 2) && (x < (Math.PI) / 2))
         {
             int n =1;

             double summm=0;
             double Psummm=-100;
             while (summm - Psummm > 0.01)
             {
                 Psummm=summm;
                summm+=( (BernulliNumbe(2*n))*(stepen(-4,n))*(1+stepen(-4,n))/((Factorial(2*n))*(stepen(x,2*n-1))));
                 n++;
             }
             tgx=summm;
             return true;
         }
         else
         {
             tgx = 0;
             return false;

         }
    }

        public static int Factorial(int numb)
        {
            int res = 1;
            for (int i = numb; i > 1; i--)
                res *= i;
            return res;
        }



    }
}