#include <iostream>
using namespace std; 
int h=0;
void hanNuo(int n,char a,char b,char c){
    if(n > 0){
        hanNuo(n - 1,a,c,b);
        h++;
        hanNuo(n - 1,b,a,c);        
    }
}
   
int main(){
    int n;
    cin>>n;
    hanNuo(n,'A','B','C');
    cout<<h;
}
/**************************************************************
	Problem: 1223
	User: chenzhuo1
	Language: C++
	Result: Accepted
	Time:8 ms
	Memory:2072 kb
****************************************************************/