题解 | #大吉大利，今晚吃鸡#

#include <stdio.h>
int num(int x)//类似汉诺塔的题目，找到规律
{
    if(x == 1)
    return 2;
    else
    return  num(x - 1) * 3 + 2;    
}

int main() {
    int n;
    while(scanf("%d\n",&n)==1)
    {
        printf("%d\n",num(n));
    }
    return 0;
}