namespace FibonacciLibrary
{
    public class FibEx
    {
        public void GetFibNumber(int n)
        {
            if (n <= 1)
                throw new FibonaciResultException(1.ToString());
            else
            {
                int elemOne = 0, elemTwo = 0, result = 0;

                try { GetFibNumber(n - 1); }
                catch (FibonaciResultException ex)
                {
                    elemOne = int.Parse(ex.Message);
                }

                try { GetFibNumber(n - 2); }
                catch (FibonaciResultException ex)
                {
                    elemTwo = int.Parse(ex.Message);
                }
                result = elemOne + elemTwo;

                throw new FibonaciResultException(result.ToString());
            }
        }
    }

    internal class FibonaciResultException : Exception
    {

        public FibonaciResultException(string message)
        : base(message) { }
    }
}