#include<stdio.h>

int main(){
    int units;
    float bill;
    
    scanf("%d",&units);
    
    if(Unit<0){
        printf("Invalid input");
    }
    else if(Units <= 100){
        bill = Units*0.10;
        printf("%.2f",bill);
    }
    else if (Units <= 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;
    
}