import java.util.*;

public class Main {

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		long A = sc.nextLong();
		String B = sc.next();
		sc.close();
		int B100 = 0;
		B100 += Integer.parseInt(B.substring(0, 1)) * 100;
		B100 += Integer.parseInt(B.substring(2, 3)) * 10;
		B100 += Integer.parseInt(B.substring(3, 4)) * 1;
		System.out.println((long) A * B100 / 100);
	}
} import java.util.*; util.* java public class Main {

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		long A = sc.nextLong();
		String B = sc.next();
		sc.close();
		int B100 = 0;
		B100 += Integer.parseInt(B.substring(0, 1)) * 100;
		B100 += Integer.parseInt(B.substring(2, 3)) * 10;
		B100 += Integer.parseInt(B.substring(3, 4)) * 1;
		System.out.println((long) A * B100 / 100);
	}
} Main public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		long A = sc.nextLong();
		String B = sc.next();
		sc.close();
		int B100 = 0;
		B100 += Integer.parseInt(B.substring(0, 1)) * 100;
		B100 += Integer.parseInt(B.substring(2, 3)) * 10;
		B100 += Integer.parseInt(B.substring(3, 4)) * 1;
		System.out.println((long) A * B100 / 100);
	} main {
		Scanner sc = new Scanner(System.in);
		long A = sc.nextLong();
		String B = sc.next();
		sc.close();
		int B100 = 0;
		B100 += Integer.parseInt(B.substring(0, 1)) * 100;
		B100 += Integer.parseInt(B.substring(2, 3)) * 10;
		B100 += Integer.parseInt(B.substring(3, 4)) * 1;
		System.out.println((long) A * B100 / 100);
	} Scanner sc = new Scanner(System.in); sc new Scanner(System.in) long A = sc.nextLong(); A sc.nextLong() sc.nextLong sc String B = sc.next(); B sc.next() sc.next sc sc.close() sc.close sc int B100 = 0; B100 0 B100 += Integer.parseInt(B.substring(0, 1)) * 100 B100 Integer.parseInt(B.substring(0, 1)) * 100 Integer.parseInt(B.substring(0, 1)) Integer.parseInt Integer B.substring(0, 1) B.substring B 0 1 100 B100 += Integer.parseInt(B.substring(2, 3)) * 10 B100 Integer.parseInt(B.substring(2, 3)) * 10 Integer.parseInt(B.substring(2, 3)) Integer.parseInt Integer B.substring(2, 3) B.substring B 2 3 10 B100 += Integer.parseInt(B.substring(3, 4)) * 1 B100 Integer.parseInt(B.substring(3, 4)) * 1 Integer.parseInt(B.substring(3, 4)) Integer.parseInt Integer B.substring(3, 4) B.substring B 3 4 1 System.out.println((long) A * B100 / 100) System.out.println System.out System System.out (long) A * B100 / 100 (long) A * B100 (long) A B100 100 String[] args args public class Main {

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		long A = sc.nextLong();
		String B = sc.next();
		sc.close();
		int B100 = 0;
		B100 += Integer.parseInt(B.substring(0, 1)) * 100;
		B100 += Integer.parseInt(B.substring(2, 3)) * 10;
		B100 += Integer.parseInt(B.substring(3, 4)) * 1;
		System.out.println((long) A * B100 / 100);
	}
} public class Main {

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		long A = sc.nextLong();
		String B = sc.next();
		sc.close();
		int B100 = 0;
		B100 += Integer.parseInt(B.substring(0, 1)) * 100;
		B100 += Integer.parseInt(B.substring(2, 3)) * 10;
		B100 += Integer.parseInt(B.substring(3, 4)) * 1;
		System.out.println((long) A * B100 / 100);
	}
} Main
import java.util.*;

public class Main {

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		long A = sc.nextLong();
		String B = sc.next();
		sc.close();
		int B100 = 0;
		B100 += Integer.parseInt(B.substring(0, 1)) * 100;
		B100 += Integer.parseInt(B.substring(2, 3)) * 10;
		B100 += Integer.parseInt(B.substring(3, 4)) * 1;
		System.out.println((long) A * B100 / 100);
	}
}
