#include <bits/stdc++.h>
using namespace std;
typedef long long int ll ;
ll dp[500][5] ;
ll n ;
int main() {
cin>>n ;
//2......right..
//3.....left...
//1.................full
dp[1][1] = 0 ;
dp[1][2] = 0 ;
dp[1][3] = 0 ;
dp[2][1] = 3 ;
dp[2][2] = 1 ;
dp[2][3] = 1 ;
ll i = 3 ;
while(i<=n){
dp[i][1] = 3*dp[i-2][1] + dp[i-2][2] + dp[i-2][3] ;
dp[i][2] = dp[i-2][1] + dp[i-2][2] ;
dp[i][3] = dp[i-2][1] + dp[i-2][3] ;
i++;
}
cout<<dp[n][1] ;
return 0 ;
}