public class ViralAdvertising {
    // https://www.hackerrank.com/challenges/strange-advertising/problem

    public ViralAdvertising() {
        Scanner scanner = new Scanner(System.in);
        int n = scanner.nextInt();
        double m = Math.floor(5 / 2);
        double a = m;

        for (int i = 1 ; i < n ; i++) {
            a = Math.floor(3 * a / 2);
            m += a;
        }

        System.out.println((int)m);
    }
}