#include <bits/stdc++.h> using namespace std; int temp=0; int move(int n,char a,char b,char c) { if(n==0) { return 0; } else { move(2n-1,a,b,c); temp++; move(2n-1,b,a,c); } } int main() { int n; char a='A',b='B',c='C'; cin>>n; move(n,a,b,c); cout<<temp<<endl; return 0; }