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();
    String b[] =B.split("",0);long D;
    D =Integer.parseInt(b[0]+b[2]+b[3]);
    long E =A*D;
    long F =E/100;
    System.out.println(F);
  }
}
/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