#include<stdio.h>

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