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