public class Ketjut {
    public static long laske(int n, int k) {
        long[] tulos = new long[n+1];
        tulos[0] = 1;
        for (int i = 1; i <= n; i++) {
            for (int j = 1; j <= k; j++) {
                if (i-j < 0) break;
                tulos[i] += tulos[i-j]*3;
            }
            if (i <= k) tulos[i]++;
        }
        return tulos[n];
    }

    public static void main(String[] args) {
        System.out.println(laske(30, 5));
    }
}