#include<stdio.h>
int main(){
    int units;
    float bills=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;
}