#include <iostream> using namespace std; int main(){ int m; double s=0; cin>>m; if(m<=2){ s=6; }else{ if(m>2&&m<=10){ s=6+(m-2)*1.8; }else{ if(m>10){ s=6+(m-2)*1.8+(m-10)*1.8*1.5; } } } cout<<s<<endl; }