题解 | #大吉大利，今晚吃鸡#

#include<stdio.h>
int main() {
    int n;
    while (~scanf("%d", &n)) {
        int a = 1;
        for (int i = 1; i <= n; i++)
            a *= 3;        
        printf("%d\n", a - 1);
    }
    return 0;
}