import java.util.Scanner;

public class Main {

	public static void main(String[] args) {

		Scanner scan = new Scanner(System.in);

		long A = scan.nextLong();
		int B =(int)(scan.nextDouble()*100+0.05);

		long ans =(A * B) / 100;
		System.out.println(ans);
		scan.close();
	}

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

	public static void main(String[] args) {

		Scanner scan = new Scanner(System.in);

		long A = scan.nextLong();
		int B =(int)(scan.nextDouble()*100+0.05);

		long ans =(A * B) / 100;
		System.out.println(ans);
		scan.close();
	}

} Main public static void main(String[] args) {

		Scanner scan = new Scanner(System.in);

		long A = scan.nextLong();
		int B =(int)(scan.nextDouble()*100+0.05);

		long ans =(A * B) / 100;
		System.out.println(ans);
		scan.close();
	} main {

		Scanner scan = new Scanner(System.in);

		long A = scan.nextLong();
		int B =(int)(scan.nextDouble()*100+0.05);

		long ans =(A * B) / 100;
		System.out.println(ans);
		scan.close();
	} Scanner scan = new Scanner(System.in); scan new Scanner(System.in) long A = scan.nextLong(); A scan.nextLong() scan.nextLong scan int B =(int)(scan.nextDouble()*100+0.05); B (int)(scan.nextDouble()*100+0.05) scan.nextDouble()*100 scan.nextDouble() scan.nextDouble scan 100 0.05 long ans =(A * B) / 100; ans (A * B) / 100 (A * B) A B 100 System.out.println(ans) System.out.println System.out System System.out ans scan.close() scan.close scan String[] args args public class Main {

	public static void main(String[] args) {

		Scanner scan = new Scanner(System.in);

		long A = scan.nextLong();
		int B =(int)(scan.nextDouble()*100+0.05);

		long ans =(A * B) / 100;
		System.out.println(ans);
		scan.close();
	}

} public class Main {

	public static void main(String[] args) {

		Scanner scan = new Scanner(System.in);

		long A = scan.nextLong();
		int B =(int)(scan.nextDouble()*100+0.05);

		long ans =(A * B) / 100;
		System.out.println(ans);
		scan.close();
	}

} Main
import java.util.Scanner;

public class Main {

	public static void main(String[] args) {

		Scanner scan = new Scanner(System.in);

		long A = scan.nextLong();
		int B =(int)(scan.nextDouble()*100+0.05);

		long ans =(A * B) / 100;
		System.out.println(ans);
		scan.close();
	}

}
