#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("%.2f",bill);
    return 0;
 
    
}