#include<bits/stdc++.h>
using namespace std;
long long f(long long  n){
	if(n==1)return 1;
	else if(n==2) return 2;
	else return 2*f(n-1)+f(n-2);
}
int main(){
	int n;
	cin>>n;
	cout<<f(n) ;


	return 0;
}



/**************************************************************
	Problem: 1369
	User: hulaoshi
	Language: C++
	Result: Time Limit Exceed
****************************************************************/