include <bits/stdc++.h>

using namespace std;

int main() {

double a, b, c;
cin >> a;
if (a <= 20) {
	b = ceil(a);
	c = b * 1.68;
	printf("%.2lf", c);
} else {
	b = ceil(a);
	c = (b - 20) * 1.98 + 33.6;
	printf("%.2lf", c);
}
return 0;

}