include <stdio.h>

int main() { double a, b, c; int d; scanf("%lf", &a); d = a + 0.99999; if (d <= 20) {

c = d * 1.68;
printf("%.2lf", c);

} if (d > 20) {

b = (d - 20) * 1.98 + 20 * 1.68;
printf("%.2lf", b);

}

return 0; }