include<bits/stdc++.h>

using namespace std; int main() {

double a;
double c, d, e;
scanf("%lf", &a);
int _=ceil(a);
if(a <= 20)
{
    c = _*1.68;
    printf("%.2lf", c);
}
else
{
    d = (_ - 20) * 1.98;
    e = 20 * 1.68 + d;
    printf("%.2lf", e);
}
return 0;

}