#include<bits/stdc++.h> using namespace std; int main(){ int a; cin>>a; if(a<=2){ cout<<6; }else { if(a>2 && a <=10){ cout<<6 + (a-2)* 1.8; }else{ cout<<6+8*1.8+(a-10)*1.8*1.5; } } return 0; }