import java.util.*;

class Main{
  public static void main(String[] args){
    Scanner sc=new Scanner(System.in);
    long a=sc.nextLong();
    long b=(long)(sc.nextDouble()*100+0.5);
    System.out.println(a*b/100);
  }
} import java.util.*; util.* java class Main{
  public static void main(String[] args){
    Scanner sc=new Scanner(System.in);
    long a=sc.nextLong();
    long b=(long)(sc.nextDouble()*100+0.5);
    System.out.println(a*b/100);
  }
} Main public static void main(String[] args){
    Scanner sc=new Scanner(System.in);
    long a=sc.nextLong();
    long b=(long)(sc.nextDouble()*100+0.5);
    System.out.println(a*b/100);
  } main {
    Scanner sc=new Scanner(System.in);
    long a=sc.nextLong();
    long b=(long)(sc.nextDouble()*100+0.5);
    System.out.println(a*b/100);
  } Scanner sc=new Scanner(System.in); sc new Scanner(System.in) long a=sc.nextLong(); a sc.nextLong() sc.nextLong sc long b=(long)(sc.nextDouble()*100+0.5); b (long)(sc.nextDouble()*100+0.5) sc.nextDouble()*100 sc.nextDouble() sc.nextDouble sc 100 0.5 System.out.println(a*b/100) System.out.println System.out System System.out a*b/100 a*b a b 100 String[] args args
import java.util.*;

class Main{
  public static void main(String[] args){
    Scanner sc=new Scanner(System.in);
    long a=sc.nextLong();
    long b=(long)(sc.nextDouble()*100+0.5);
    System.out.println(a*b/100);
  }
}
