import java.util.*;

public class Main {
  public static void main(String[] args) {
    Scanner sc = new Scanner(System.in);
    long a = sc.nextLong();
    double b = sc.nextDouble();
    long B = (long)(b * (double)100 + 0.01);
    System.out.println((a * B) / (long)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();
    double b = sc.nextDouble();
    long B = (long)(b * (double)100 + 0.01);
    System.out.println((a * B) / (long)100);
  }
} Main public static void main(String[] args) {
    Scanner sc = new Scanner(System.in);
    long a = sc.nextLong();
    double b = sc.nextDouble();
    long B = (long)(b * (double)100 + 0.01);
    System.out.println((a * B) / (long)100);
  } main {
    Scanner sc = new Scanner(System.in);
    long a = sc.nextLong();
    double b = sc.nextDouble();
    long B = (long)(b * (double)100 + 0.01);
    System.out.println((a * B) / (long)100);
  } Scanner sc = new Scanner(System.in); sc new Scanner(System.in) long a = sc.nextLong(); a sc.nextLong() sc.nextLong sc double b = sc.nextDouble(); b sc.nextDouble() sc.nextDouble sc long B = (long)(b * (double)100 + 0.01); B (long)(b * (double)100 + 0.01) b * (double)100 b (double)100 0.01 System.out.println((a * B) / (long)100) System.out.println System.out System System.out (a * B) / (long)100 (a * B) a B (long)100 String[] args args public class Main {
  public static void main(String[] args) {
    Scanner sc = new Scanner(System.in);
    long a = sc.nextLong();
    double b = sc.nextDouble();
    long B = (long)(b * (double)100 + 0.01);
    System.out.println((a * B) / (long)100);
  }
} public class Main {
  public static void main(String[] args) {
    Scanner sc = new Scanner(System.in);
    long a = sc.nextLong();
    double b = sc.nextDouble();
    long B = (long)(b * (double)100 + 0.01);
    System.out.println((a * B) / (long)100);
  }
} Main
import java.util.*;

public class Main {
  public static void main(String[] args) {
    Scanner sc = new Scanner(System.in);
    long a = sc.nextLong();
    double b = sc.nextDouble();
    long B = (long)(b * (double)100 + 0.01);
    System.out.println((a * B) / (long)100);
  }
}