import java.util.Scanner;

public class Main {

	public static void main(String[] args) {

		Scanner scan = new Scanner(System.in);

		long A = scan.nextLong();
		float B = scan.nextFloat();

		long ans = (A * ((long)(B * 100 + 0.5))) / 100;

		System.out.println(ans);

	}
} 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();
		float B = scan.nextFloat();

		long ans = (A * ((long)(B * 100 + 0.5))) / 100;

		System.out.println(ans);

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

		Scanner scan = new Scanner(System.in);

		long A = scan.nextLong();
		float B = scan.nextFloat();

		long ans = (A * ((long)(B * 100 + 0.5))) / 100;

		System.out.println(ans);

	} main {

		Scanner scan = new Scanner(System.in);

		long A = scan.nextLong();
		float B = scan.nextFloat();

		long ans = (A * ((long)(B * 100 + 0.5))) / 100;

		System.out.println(ans);

	} Scanner scan = new Scanner(System.in); scan new Scanner(System.in) long A = scan.nextLong(); A scan.nextLong() scan.nextLong scan float B = scan.nextFloat(); B scan.nextFloat() scan.nextFloat scan long ans = (A * ((long)(B * 100 + 0.5))) / 100; ans (A * ((long)(B * 100 + 0.5))) / 100 (A * ((long)(B * 100 + 0.5))) A ((long)(B * 100 + 0.5)) B * 100 B 100 0.5 100 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 scan = new Scanner(System.in);

		long A = scan.nextLong();
		float B = scan.nextFloat();

		long ans = (A * ((long)(B * 100 + 0.5))) / 100;

		System.out.println(ans);

	}
} public class Main {

	public static void main(String[] args) {

		Scanner scan = new Scanner(System.in);

		long A = scan.nextLong();
		float B = scan.nextFloat();

		long ans = (A * ((long)(B * 100 + 0.5))) / 100;

		System.out.println(ans);

	}
} Main
import java.util.Scanner;

public class Main {

	public static void main(String[] args) {

		Scanner scan = new Scanner(System.in);

		long A = scan.nextLong();
		float B = scan.nextFloat();

		long ans = (A * ((long)(B * 100 + 0.5))) / 100;

		System.out.println(ans);

	}
}