#include<bits/stdc++.h> using namespace std; int main(){ double sumi=0,s; cin>>s; if (s<=2){ sumi+=6; } else if (s<=10){ sumi+=6+(s-2)*1.8; } else{ sumi+=6+8*1.8+(s-10)*1.8*1.5; } cout<<sumi<<endl; return 0; }