#include<stdio.h>
int main(){
    int n;
    float bill=0.0;
    scanf("%d",&n)
    if(n<0){
        printf("Invalid input");
        return 0;
    }
    if(n<=100){
        bill=n*0.10;
    }
    else if(n<=200){
        bill=100*0.10+(n-100)*0.15;
    }
    else{
        bill=100*0.10+100*0.15+(n-200)*0.20;
    }
    printf("%.2f",bill);
    return 0;
}