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