import java.util.Scanner;

public class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		long A = sc.nextLong();
		String sB = sc.next();
		long B = Integer.parseInt(sB.substring(0, 1)) * 100 +
				 Integer.parseInt(sB.substring(2, 3)) * 10 +
				 Integer.parseInt(sB.substring(3, 4));
		System.out.println((A * B / 100));

		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();
		String sB = sc.next();
		long B = Integer.parseInt(sB.substring(0, 1)) * 100 +
				 Integer.parseInt(sB.substring(2, 3)) * 10 +
				 Integer.parseInt(sB.substring(3, 4));
		System.out.println((A * B / 100));

		sc.close();
	}
} Main public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		long A = sc.nextLong();
		String sB = sc.next();
		long B = Integer.parseInt(sB.substring(0, 1)) * 100 +
				 Integer.parseInt(sB.substring(2, 3)) * 10 +
				 Integer.parseInt(sB.substring(3, 4));
		System.out.println((A * B / 100));

		sc.close();
	} main {
		Scanner sc = new Scanner(System.in);
		long A = sc.nextLong();
		String sB = sc.next();
		long B = Integer.parseInt(sB.substring(0, 1)) * 100 +
				 Integer.parseInt(sB.substring(2, 3)) * 10 +
				 Integer.parseInt(sB.substring(3, 4));
		System.out.println((A * B / 100));

		sc.close();
	} Scanner sc = new Scanner(System.in); sc new Scanner(System.in) long A = sc.nextLong(); A sc.nextLong() sc.nextLong sc String sB = sc.next(); sB sc.next() sc.next sc long B = Integer.parseInt(sB.substring(0, 1)) * 100 +
				 Integer.parseInt(sB.substring(2, 3)) * 10 +
				 Integer.parseInt(sB.substring(3, 4)); B Integer.parseInt(sB.substring(0, 1)) * 100 +
				 Integer.parseInt(sB.substring(2, 3)) * 10 +
				 Integer.parseInt(sB.substring(3, 4)) Integer.parseInt(sB.substring(0, 1)) * 100 +
				 Integer.parseInt(sB.substring(2, 3)) * 10 +
				 Integer.parseInt(sB.substring(3, 4)) Integer.parseInt(sB.substring(0, 1)) * 100 Integer.parseInt(sB.substring(0, 1)) Integer.parseInt Integer sB.substring(0, 1) sB.substring sB 0 1 100 Integer.parseInt(sB.substring(2, 3)) * 10 Integer.parseInt(sB.substring(2, 3)) Integer.parseInt Integer sB.substring(2, 3) sB.substring sB 2 3 10 Integer.parseInt(sB.substring(3, 4)) Integer.parseInt Integer sB.substring(3, 4) sB.substring sB 3 4 System.out.println((A * B / 100)) System.out.println System.out System System.out (A * B / 100) A * B A B 100 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();
		String sB = sc.next();
		long B = Integer.parseInt(sB.substring(0, 1)) * 100 +
				 Integer.parseInt(sB.substring(2, 3)) * 10 +
				 Integer.parseInt(sB.substring(3, 4));
		System.out.println((A * B / 100));

		sc.close();
	}
} public class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		long A = sc.nextLong();
		String sB = sc.next();
		long B = Integer.parseInt(sB.substring(0, 1)) * 100 +
				 Integer.parseInt(sB.substring(2, 3)) * 10 +
				 Integer.parseInt(sB.substring(3, 4));
		System.out.println((A * B / 100));

		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();
		String sB = sc.next();
		long B = Integer.parseInt(sB.substring(0, 1)) * 100 +
				 Integer.parseInt(sB.substring(2, 3)) * 10 +
				 Integer.parseInt(sB.substring(3, 4));
		System.out.println((A * B / 100));

		sc.close();
	}
}
