import java.util.Scanner;

public class Main{
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		
		long a = Long.parseLong(sc.next());
		double b = Double.parseDouble(sc.next());
		long c = (long)Math.round(b*100);
		a = a * c;
		a /= 100;
		System.out.println(a);
		
	}


} import java.util.Scanner; Scanner java.util public class Main{
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		
		long a = Long.parseLong(sc.next());
		double b = Double.parseDouble(sc.next());
		long c = (long)Math.round(b*100);
		a = a * c;
		a /= 100;
		System.out.println(a);
		
	}


} Main public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		
		long a = Long.parseLong(sc.next());
		double b = Double.parseDouble(sc.next());
		long c = (long)Math.round(b*100);
		a = a * c;
		a /= 100;
		System.out.println(a);
		
	} main {
		Scanner sc = new Scanner(System.in);
		
		long a = Long.parseLong(sc.next());
		double b = Double.parseDouble(sc.next());
		long c = (long)Math.round(b*100);
		a = a * c;
		a /= 100;
		System.out.println(a);
		
	} Scanner sc = new Scanner(System.in); sc new Scanner(System.in) long a = Long.parseLong(sc.next()); a Long.parseLong(sc.next()) Long.parseLong Long sc.next() sc.next sc double b = Double.parseDouble(sc.next()); b Double.parseDouble(sc.next()) Double.parseDouble Double sc.next() sc.next sc long c = (long)Math.round(b*100); c (long)Math.round(b*100) Math.round Math b*100 b 100 a = a * c a a * c a c a /= 100 a 100 System.out.println(a) System.out.println System.out System System.out a String[] args args public class Main{
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		
		long a = Long.parseLong(sc.next());
		double b = Double.parseDouble(sc.next());
		long c = (long)Math.round(b*100);
		a = a * c;
		a /= 100;
		System.out.println(a);
		
	}


} public class Main{
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		
		long a = Long.parseLong(sc.next());
		double b = Double.parseDouble(sc.next());
		long c = (long)Math.round(b*100);
		a = a * c;
		a /= 100;
		System.out.println(a);
		
	}


} Main
import java.util.Scanner;

public class Main{
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		
		long a = Long.parseLong(sc.next());
		double b = Double.parseDouble(sc.next());
		long c = (long)Math.round(b*100);
		a = a * c;
		a /= 100;
		System.out.println(a);
		
	}


}
