using System;

public class Program

{

    public static void Main()

    {

          int NthNumber = 10;

            //Decrement the Nth Number by 1. This is because the series starts with 0

            NthNumber = NthNumber - 1;

            Console.Write(NthFibonacciNumber(NthNumber));

            Console.ReadKey();

        }

        private static int NthFibonacciNumber(int number)

        {

            int firstNumber = 0, secondNumber = 1, nextNumber = 0;

            // To return the first Fibonacci number  

            if (number == 0)

                return firstNumber;

            for (int i = 2; i <= number; i++)

            {

                nextNumber = firstNumber + secondNumber;

                firstNumber = secondNumber;

                secondNumber = nextNumber;

            }

            return secondNumber;

        }

}