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