Some friends are playing hide-and-seek (捉迷藏) at Mr. Green’ home. They play in Mike’s room. It’s time for Lily to find her friends. Lily first finds Sally.Sally is behind the door. Then, Lily sees Bob. Bob is under the table. Mike is under the table, too. Now it’s time to find David and John. David’s hat is on the sofa. Is David under the sofa? No, he isn’t.John’s schoolbag is on the chair, but he isn’t there.“Where are they?”Lily thinks.Shh! Don’t let her know. They are under the bed!

一Don't worry. We all know that failure is the mother of ____.

根据国务院办公厅印发的《全面推进河长制的建议》，到2018年6月底，我国要在省、市、县、乡四级，全面建立河长制。建立“河长制”，是为了早日实现“河长治”。据此回答小题。