#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 * 0.10)+(100 * 0.15) + ((units-200)*0.20)

    printf("%2f", bill);
    
    return 0;
}