package m.shin;
import java.math.BigDecimal;
import java.util.Scanner;
public class Con350 {

	public static void main(String[] args) {
		Scanner s = new Scanner(System.in);
		BigDecimal v = new BigDecimal(s.next()) , t = new BigDecimal(s.next());
		s.close();

		v = v.multiply(t).setScale(0, BigDecimal.ROUND_DOWN);
		System.out.println(v.toString());
	}

}