namespace ConsoleApplication2
{
    class Program
    {

        static long factorial(long n)
        {
            long toReturn = 1;
            for (int i = 2; i <= n; i++) {
                toReturn *= i;
            }

            return toReturn;
        }

        static void Main(string[] args)
        {
            double suma = 0.0;
            long x = 90;
            int k = 10;
            for (int i = 0; i <= k; i++)
            {
                suma += (Math.Pow(-1, k) * Math.Pow(x, 2 * k + 1)) / factorial(2 * k + 1);
            }
            Console.WriteLine(suma);
        }
    }
}