#include<iostream>
#include<vector>
#include<algorithm>
#include<string>
#include<math.h>
using namespace std;

long long prob5(int n);
int main()
{
   int vount=prob5(4);
   cout<<endl<<vount;
   getchar();
   return 0;
}


long long prob5(int n)
{
    
    long long vount=(pow(3,n)+1)/2;
    return vount;
    
}