#include<bits/stdc++.h> using namespace std; int main(){ double feiyong,zhongliang; cin>>zhongliang; if(zhongliang<=10.0){ feiyong=zhongliang*2.5; } else if(zhongliang>10.0){ feiyong=25.0+((zhongliang-10.0)*1.5); } printf("%.1lf",feiyong); return 0; }