import java.util.*;

public class Main{
    public static void main(String[] args){
        Scanner scan = new java.util.Scanner(System.in);
        long a = scan.nextLong();
        String bs = scan.next();
        int b = Integer.parseInt(Character.toString((bs.charAt(0)))) * 100
                + Integer.parseInt(Character.toString((bs.charAt(2)))) * 10
                + Integer.parseInt(Character.toString((bs.charAt(3))));
        System.out.println((long)a * b / 100);
        scan.close();
    }
} import java.util.*; util.* java public class Main{
    public static void main(String[] args){
        Scanner scan = new java.util.Scanner(System.in);
        long a = scan.nextLong();
        String bs = scan.next();
        int b = Integer.parseInt(Character.toString((bs.charAt(0)))) * 100
                + Integer.parseInt(Character.toString((bs.charAt(2)))) * 10
                + Integer.parseInt(Character.toString((bs.charAt(3))));
        System.out.println((long)a * b / 100);
        scan.close();
    }
} Main public static void main(String[] args){
        Scanner scan = new java.util.Scanner(System.in);
        long a = scan.nextLong();
        String bs = scan.next();
        int b = Integer.parseInt(Character.toString((bs.charAt(0)))) * 100
                + Integer.parseInt(Character.toString((bs.charAt(2)))) * 10
                + Integer.parseInt(Character.toString((bs.charAt(3))));
        System.out.println((long)a * b / 100);
        scan.close();
    } main {
        Scanner scan = new java.util.Scanner(System.in);
        long a = scan.nextLong();
        String bs = scan.next();
        int b = Integer.parseInt(Character.toString((bs.charAt(0)))) * 100
                + Integer.parseInt(Character.toString((bs.charAt(2)))) * 10
                + Integer.parseInt(Character.toString((bs.charAt(3))));
        System.out.println((long)a * b / 100);
        scan.close();
    } Scanner scan = new java.util.Scanner(System.in); scan new java.util.Scanner(System.in) long a = scan.nextLong(); a scan.nextLong() scan.nextLong scan String bs = scan.next(); bs scan.next() scan.next scan int b = Integer.parseInt(Character.toString((bs.charAt(0)))) * 100
                + Integer.parseInt(Character.toString((bs.charAt(2)))) * 10
                + Integer.parseInt(Character.toString((bs.charAt(3)))); b Integer.parseInt(Character.toString((bs.charAt(0)))) * 100
                + Integer.parseInt(Character.toString((bs.charAt(2)))) * 10
                + Integer.parseInt(Character.toString((bs.charAt(3)))) Integer.parseInt(Character.toString((bs.charAt(0)))) * 100
                + Integer.parseInt(Character.toString((bs.charAt(2)))) * 10
                + Integer.parseInt(Character.toString((bs.charAt(3)))) Integer.parseInt(Character.toString((bs.charAt(0)))) * 100 Integer.parseInt(Character.toString((bs.charAt(0)))) Integer.parseInt Integer Character.toString((bs.charAt(0))) Character.toString Character (bs.charAt(0)) bs.charAt bs 0 100 Integer.parseInt(Character.toString((bs.charAt(2)))) * 10 Integer.parseInt(Character.toString((bs.charAt(2)))) Integer.parseInt Integer Character.toString((bs.charAt(2))) Character.toString Character (bs.charAt(2)) bs.charAt bs 2 10 Integer.parseInt(Character.toString((bs.charAt(3)))) Integer.parseInt Integer Character.toString((bs.charAt(3))) Character.toString Character (bs.charAt(3)) bs.charAt bs 3 System.out.println((long)a * b / 100) System.out.println System.out System System.out (long)a * b / 100 (long)a * b (long)a b 100 scan.close() scan.close scan String[] args args public class Main{
    public static void main(String[] args){
        Scanner scan = new java.util.Scanner(System.in);
        long a = scan.nextLong();
        String bs = scan.next();
        int b = Integer.parseInt(Character.toString((bs.charAt(0)))) * 100
                + Integer.parseInt(Character.toString((bs.charAt(2)))) * 10
                + Integer.parseInt(Character.toString((bs.charAt(3))));
        System.out.println((long)a * b / 100);
        scan.close();
    }
} public class Main{
    public static void main(String[] args){
        Scanner scan = new java.util.Scanner(System.in);
        long a = scan.nextLong();
        String bs = scan.next();
        int b = Integer.parseInt(Character.toString((bs.charAt(0)))) * 100
                + Integer.parseInt(Character.toString((bs.charAt(2)))) * 10
                + Integer.parseInt(Character.toString((bs.charAt(3))));
        System.out.println((long)a * b / 100);
        scan.close();
    }
} Main
import java.util.*;

public class Main{
    public static void main(String[] args){
        Scanner scan = new java.util.Scanner(System.in);
        long a = scan.nextLong();
        String bs = scan.next();
        int b = Integer.parseInt(Character.toString((bs.charAt(0)))) * 100
                + Integer.parseInt(Character.toString((bs.charAt(2)))) * 10
                + Integer.parseInt(Character.toString((bs.charAt(3))));
        System.out.println((long)a * b / 100);
        scan.close();
    }
}