题解 | #大吉大利，今晚吃鸡#

int main() {
    int n;
    while (scanf("%d", &n) != EOF) {
        int m = 1;
        for (int i = 0; i < n; i++)
            m *= 3;
        printf("%d\n", m - 1);
    }
    return 0;
}