#include <stdio.h>
int main() {
    int units;
    float bill = 0;
    if (scanf("%d", &units) != 1 || units < 0) {
        printf("Invalid input");
        return 0;
    }
    if (units <= 100)
        bill = units * 0.10;
    else if (unit <= 200)
        bill = 100 * 0.10 + (units - 100) * 0.15;
    else
        bill = 100 * 0.10 + 100 * 0.15 + (units - 200) * 0.20;
        printf("%.2f", bill);
        return 0;
}