#include<iostream> using namespace std; int main(){ int a; cin>>a; if(a <=2){ cout<<6<<endl; } if(a>2 && a <=10){ printf("%.1f",6+(a-2)*1.8); } if(a>10){ printf("%.1f",6+(10-2)*1.8 + (a-10)*1.5*1.8); } return 0; }