include<bits/stdc++.h>

include <math.h>

using namespace std; int main() {

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

}