#include<iostream> #include<cstdio> using namespace std; int main(){ int t; cin>>t; if(t<2){ cout<<6<<endl; } else if(t<10){ cout<<(t-2)*1.8+6<<endl; } else{ cout<<(t-10)*1.8*1.5+(10-2)*1.8+6<<endl; } return 0; }