#include<bits/stdc++.h> using namespace std; int main() { int lu; cin>>lu; if(lu<=2){ cout<<6; return 0; } if(10>=lu&&lu>2){ cout<<6+(lu-2)*1.8; return 0; } if(lu>10){ cout<<6+(10-2)*1.8+(lu-10)*(1.8*0.5+1.8); } return 0; }