import java.util.*;
class Main
{
    public static void main(String[] args)
    {
        Scanner sc=new Scanner(System.in);
        int sal=sc.nextInt();
        int ye=sc.nextInt();
        if(sal<0)
        {
            System.out.print("Invalid input");
            return;
        }
        double b;
        if(ye<2)
        {
            b=0;
        }
        else if(ye>=2 && ye<=5)
        {
            b=sal*5/100;
        }
        else if(ye>5)
        {
            b=sal*10/100;
        }
        System.out.printf("%.1f",b);
    }
}