#include <iostream>
#include <cstdio>
#include <cstring>
#include <cmath>
#include <cstdlib>
#include <algorithm>
using namespace std;
long long  a[55];

int main ()
{
	memset(a,1,sizeof(a));
	a[1]=3;
	a[2]=8;
	for(int i=3;i<=50;i++)
	{
		a[i]=2*(a[i-1]+a[i-2]);
	}
	long long n;
	while(scanf("%lld",&n)==1 && n>0 && n<=50)
	{
		printf("%lld\n",a[n]);
	}
	return 0;
}