import java.util.*;
public class Main {
	public static void main(String[] args){
      Scanner sc = new Scanner(System.in);
      long A = sc.nextLong();
      String b = sc.next();
      String B = b.substring(0,1)+b.substring(2,4);
      int C =Integer.parseInt(B);
      long D = A*C;
      System.out.println(D/100);
	}
} import java.util.*; util.* java public class Main {
	public static void main(String[] args){
      Scanner sc = new Scanner(System.in);
      long A = sc.nextLong();
      String b = sc.next();
      String B = b.substring(0,1)+b.substring(2,4);
      int C =Integer.parseInt(B);
      long D = A*C;
      System.out.println(D/100);
	}
} Main public static void main(String[] args){
      Scanner sc = new Scanner(System.in);
      long A = sc.nextLong();
      String b = sc.next();
      String B = b.substring(0,1)+b.substring(2,4);
      int C =Integer.parseInt(B);
      long D = A*C;
      System.out.println(D/100);
	} main {
      Scanner sc = new Scanner(System.in);
      long A = sc.nextLong();
      String b = sc.next();
      String B = b.substring(0,1)+b.substring(2,4);
      int C =Integer.parseInt(B);
      long D = A*C;
      System.out.println(D/100);
	} Scanner sc = new Scanner(System.in); sc new Scanner(System.in) long A = sc.nextLong(); A sc.nextLong() sc.nextLong sc String b = sc.next(); b sc.next() sc.next sc String B = b.substring(0,1)+b.substring(2,4); B b.substring(0,1)+b.substring(2,4) b.substring(0,1) b.substring b 0 1 b.substring(2,4) b.substring b 2 4 int C =Integer.parseInt(B); C Integer.parseInt(B) Integer.parseInt Integer B long D = A*C; D A*C A C System.out.println(D/100) System.out.println System.out System System.out D/100 D 100 String[] args args public class Main {
	public static void main(String[] args){
      Scanner sc = new Scanner(System.in);
      long A = sc.nextLong();
      String b = sc.next();
      String B = b.substring(0,1)+b.substring(2,4);
      int C =Integer.parseInt(B);
      long D = A*C;
      System.out.println(D/100);
	}
} public class Main {
	public static void main(String[] args){
      Scanner sc = new Scanner(System.in);
      long A = sc.nextLong();
      String b = sc.next();
      String B = b.substring(0,1)+b.substring(2,4);
      int C =Integer.parseInt(B);
      long D = A*C;
      System.out.println(D/100);
	}
} Main
import java.util.*;
public class Main {
	public static void main(String[] args){
      Scanner sc = new Scanner(System.in);
      long A = sc.nextLong();
      String b = sc.next();
      String B = b.substring(0,1)+b.substring(2,4);
      int C =Integer.parseInt(B);
      long D = A*C;
      System.out.println(D/100);
	}
}