public class Exponential {

    public static void main(String[] args) {

	long time = System.currentTimeMillis();
        long n = Long.parseLong(args[0]);
        long total = 0;

	total = exp(n);

	System.out.println(total);
	System.out.println("Time elapsed: " + 
                           (System.currentTimeMillis() - time) + " ms");

    }

    private static long exp(long n) {

	if (n <= 0) {
	    return 1;
	}
	else {
	    return exp(n-1) + exp(n-1);
	}
    }
}