import java.util.Scanner;

public class Main {


    public static void main(String args[])
    {
        Scanner sc=new Scanner(System.in);
        long a =sc.nextLong();
        String s=sc.next();
        long b=(s.charAt(0)-'0')*100+(s.charAt(2)-'0')*10+(s.charAt(3)-'0');
        long c=(a*b)/100;
        System.out.println(c);

    }
}

/tmp/hf-datasets-cache/medium/datasets/42704881117311-config-parquet-and-info-qiankunmu-Project_CodeNet-896c9d36/hub/datasets--qiankunmu--Project_CodeNet_Python800_and_Java250/snapshots/c899fde44a77ba1cc14973ed3de064e4ff3aadc7/Project_CodeNet_Java250.tar.gz