#include <stdio.h>
int main() {
    int units;
    float bill = 0.0;
    
    scanf("%d", &units);
    
    if (units < 0) {
        printf("Invalid input");
        return 0;
    }
    
    
    if (units <= 100) {
        bill = units * 0.10;
    }
    else if (units <= 200) {
        bill = (100 * 0.10) + (units - 100)* 0.15;
    }
    else {
        bill = (100 * 0.10) + (100 * 0.15) + (units - 200) * 0.20;
    }
    printf("%d.2f", bill);
    
    return 0;
}