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