class Fibonacci
{
   public static long fib(int n)
   {
      if(n < 2)
      {
         return n;
      }
      else
      {
         return (fib(n-1) + fib(n-2));
      }
   }

   public static void main(String[] args)
   {
      System.out.println(fib(Integer.parseInt(args[0])));
   }
}