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);

    }
} import java.util.Scanner; Scanner java.util 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);

    }
} 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);

    } main {
        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);

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

    }
} 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);

    }
} Main
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);

    }
}
