import java.util.*;
public class emp{
    public static void main(String[] args){
    Scanner sc=new Scanner(System.in);
    int bonus=0;
float sal=sc.nextFloat();
    int exp=sc.nextInt();
    if(sal<0){
        System.out.println("Invalid input");
        return;
    }
    else if(exp<2){
        System.out.println(sal);
    }
    else if(exp>=2 && exp<=5)
    {
        bonus=bonus*0.05f;
        System.out.printf("%.1f",bonus);
    }
    else
    {
        bonus=bonus/0.10f;
        System.out.printf("%.1f",bonus);
    }
}}