import structure5.*;

class Fib {
    /* Compute the Fibonacci number for input n.
     * This allegedly was an early model for the population
     * growth rate for rabbits (it's not actually true) although
     * the real model is not all that different.
     * Note that this would be a *great* opportunity to use
     * pre- and post- conditions.  E.g., astonishingly bad thing
     * happen when you supply -1 as an input.  How could you
     * prevent such a disaster?
     */
    public static int fibonacci(int n){
	if (n == 0) {
	    return 0;
	}
	if (n == 1) {
	    return 1;
	}
      
	return fibonacci(n - 1) +
	       fibonacci(n - 2);
    }
      
    public static void main(String[] args) {
	int n = Integer.valueOf(args[0]);
	System.out.println(fibonacci(n));
    }
}