#include<bits/stdc++.h> using namespace std; int main(){

double x;
cin>>x;
if      (x<=10) printf("%.2lf",x*0.8+0.2);
else if (x<=20) printf("%.2lf",8+(x-10)*0.75+0.2);
else if (x<=30) printf("%.2lf",15.5+(x-20)*0.7+0.2);
else cout <<"Fail";

return 0;

}