#include<stdio.h>

int main() {
    int units;
    scanf("%d", &units);
    
    if(units < 0){
        printf("Invalid input");
        return 0;
    }
    
    float bill =0.0;
    
    if (units <= 100){
        bill = units * 0.10;
    }
    else if (units <=200){
        bill =(100 * 0.10)+ (units -100) *0.15);
    }
    else{
        bill = (100* 1.10) + (100 * 0.15) + ((units - 200) * 0.20);
    }
    printf("%.2f" , bill);
    
    return 0;
}