#include<bits/stdc++.h>
using namespace std;
int w=0;
void dfs(int s,char q,char c,char z){
	if(s==1) w++;//cout<<q<<" To "<<z<<endl;
	else{
		dfs(s-1,q,z,c);
		//cout<<q<<" To "<<z<<endl;
		w++;
		dfs(s-1,c,q,z);
	}
}
int main(){
	int n;
	cin>>n;
	dfs(n,'A','B','C');
	cout<<w;
	

	return 0;
}

/**************************************************************
	Problem: 1223
	User: lidongcheng
	Language: C++
	Result: Accepted
	Time:8 ms
	Memory:2072 kb
****************************************************************/