#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;
}