#include<bits/stdc++.h> using namespace std; int main(){ double v=0; double x,m=0; cin>>x; if(x<=2){ cout<<6; } if(x<=10&&x>2){ m=1.8*(x-2)+6; cout<<m; } if(x>=10){ v=2.7*(x-10)+1.8*(x-10-2)+6; cout<<v; } return 0; }