import java.util.*;
import java.math.BigDecimal;
public class Main {
	public static void main(String[] args) {
		Scanner sc=new Scanner(System.in);
      long A=sc.nextLong();
      double B=sc.nextDouble();
      BigDecimal a=BigDecimal.valueOf(A);
      BigDecimal b=BigDecimal.valueOf(B);
      BigDecimal c=a.multiply(b);
      BigDecimal x=c.setScale(0,BigDecimal.ROUND_DOWN);
      System.out.println(x);
	}
}
/tmp/hf-datasets-cache/medium/datasets/42704881117311-config-parquet-and-info-qiankunmu-Project_CodeNet-896c9d36/hub/datasets--qiankunmu--Project_CodeNet_Python800_and_Java250/snapshots/c899fde44a77ba1cc14973ed3de064e4ff3aadc7/Project_CodeNet_Java250.tar.gz