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