public class FibRec {   
    
    private static int fib(int n){
	if (n==0) return 0;
	if (n==1) return 1;
	return fib(n-1) + fib(n-2);
    }
	

    public static void main(String[] args) {
	int n = Integer.parseInt(args[0]);
	System.out.println(fib(n));
    }
    //
    // try FibRec 40 to see a real slow down
}