import java.util.Scanner;
public class Main {

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		long a = sc.nextLong();
		double b = sc.nextDouble();
		long bb = (long)(b*100.0+0.5);
		
		long ans = (a*bb)/100;
		
		System.out.println(ans);
		sc.close();
	}

} import java.util.Scanner; Scanner 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 bb = (long)(b*100.0+0.5);
		
		long ans = (a*bb)/100;
		
		System.out.println(ans);
		sc.close();
	}

} Main public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		long a = sc.nextLong();
		double b = sc.nextDouble();
		long bb = (long)(b*100.0+0.5);
		
		long ans = (a*bb)/100;
		
		System.out.println(ans);
		sc.close();
	} main {
		Scanner sc = new Scanner(System.in);
		long a = sc.nextLong();
		double b = sc.nextDouble();
		long bb = (long)(b*100.0+0.5);
		
		long ans = (a*bb)/100;
		
		System.out.println(ans);
		sc.close();
	} 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 bb = (long)(b*100.0+0.5); bb (long)(b*100.0+0.5) b*100.0 b 100.0 0.5 long ans = (a*bb)/100; ans (a*bb)/100 (a*bb) a bb 100 System.out.println(ans) System.out.println System.out System System.out ans sc.close() sc.close sc 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 bb = (long)(b*100.0+0.5);
		
		long ans = (a*bb)/100;
		
		System.out.println(ans);
		sc.close();
	}

} public class Main {

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		long a = sc.nextLong();
		double b = sc.nextDouble();
		long bb = (long)(b*100.0+0.5);
		
		long ans = (a*bb)/100;
		
		System.out.println(ans);
		sc.close();
	}

} Main
import java.util.Scanner;
public class Main {

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		long a = sc.nextLong();
		double b = sc.nextDouble();
		long bb = (long)(b*100.0+0.5);
		
		long ans = (a*bb)/100;
		
		System.out.println(ans);
		sc.close();
	}

}