#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;
}