class Fib {

  public static int fib(int n) {
    if (n <= 1) {
      return n;
    } else {
      return fib(n-1) + fib(n-2);
    }
  }
  
  public static void main(String[] args) {
    System.out.printf("%d\n", fib(Integer.parseInt(args[0])));
  }

}