#include<bits/stdc++.h>
using namespace std;
int w;
void f(int n,char q,char c,char z){
    if(n==1)    w++;
    else{
        f(n-1,q,z,c);
        w++;
        f(n-1,c,q,z);
    }
}
int main(){
    int n;
    cin>>n;
    f(n,'A','B','C');
    cout<<w;
}
/**************************************************************
	Problem: 1223
	User: lijinkai
	Language: C++
	Result: Accepted
	Time:7 ms
	Memory:2072 kb
****************************************************************/