IMPORTANT: Please do not post solutions, hints, or other spoilers until at least 60 hours after the date of this message. Thanks. IMPORTANTE: Por favor, no enviéis soluciones, pistas, o cualquier otra cosa que pueda echar a perder la resolución del problema hasta que hayan pasado por lo menos 60 horas desde el envío de este mensaje. Gracias. IMPORTANT: S'il vous plaît, attendez au minimum 60 heures après la date de ce message avant de poster solutions, indices ou autres révélations. Merci. WICHTIG: Bitte schicken Sie keine Lösungen, Tipps oder Hinweise für diese Aufgabe vor Ablauf von 60 Stunden nach dem Datum dieser Mail. Danke. BELANGRIJK: Stuur aub geen oplossingen, hints of andere tips in de eerste 60 uur na het verzendingstijdstip van dit bericht. Waarvoor dank. VNIMANIE: Pozhalujsta ne shlite reshenija, nameki na reshenija, i voobshe lyubye podskazki v techenie po krajnej mere 60 chasov ot daty etogo soobshenija. Spasibo. Qing3 Zhu4Yi4: Qing3 Ning2 Deng3Dao4 Jie1Dao4 Ben3 Xin4Xi2 Zhi1Hou4 60 Xiao3Shi2, Zai4 Fa1Biao3 Jie3Da2, Ti2Shi4, Huo4 Qi2Ta1 Hui4 Xie4Lou4 Da2An4 De5 Jian4Yi4. Xie4Xie4. The 'MH' mail system stores email messages in a 'folder', which is just a plain directory. Messages are files in this directory whose names are numerals. The directory might contain other files or subdirectories; these are not messages. Implement a 'sortby' command that sorts the messages in a folder by subject. It should rename the messages in the folder so that (a) the set of message numbers before and after is the same, and (b) afterwards, if the subjects were extracted from each message in message number order, they would be in alphabetic order. 'sortby' is not allowed to change the contents of the folder in any other way. 'sortby' is invoked like this: sortby folder-dir [-f fieldname] [-r] 'folder-dir' is the path to the folder directory. '-f fieldname', if present, tells 'sortby' to examine the specified field of each message, instead of the subject field. '-r', if present, reverses the order of the sort. For example, here's the contents of a folder before sorting: 393 -11/18 "Barbie" use strict<