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 bb = (long) (b * 100.0 + 0.5);
		long ans = (a * bb) / 100;

		System.out.println(ans);
	}
}























 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 bb = (long) (b * 100.0 + 0.5);
		long ans = (a * bb) / 100;

		System.out.println(ans);
	}
} 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);
	} 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);
	} 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 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);
	}
} 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);
	}
} 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 bb = (long) (b * 100.0 + 0.5);
		long ans = (a * bb) / 100;

		System.out.println(ans);
	}
}
























