#include<bits/stdc++.h> using namespace std; int ans[30]={0,0,3,10,30,82,226,615,1673,4549,12366,33616,91379,248396,675213,1835420,4989190,13562026,36865411,100210580,272400599},s; int main(){ cin>>s; cout<<ans[s]; return 0; }