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