diff --git a/data/tree.json b/data/tree.json
index 44adf43e42d78b364f2e49668ac45ef27bf2877d..7ec8c1b6539d05624797a819b6c9be0049ba18cf 100644
--- a/data/tree.json
+++ b/data/tree.json
@@ -2212,4 +2212,4 @@
       }
     ]
   }
-}
\ No newline at end of file
+}
diff --git a/src/tree.py b/src/tree.py
index 61b5b8950df71658adfa6243961eab5ca45a8da2..b770efcbed27862e46454c98fa75f23c00da153b 100644
--- a/src/tree.py
+++ b/src/tree.py
@@ -14,7 +14,6 @@ formatter = logging.Formatter('%(asctime)s - %(levelname)s - %(message)s')
 handler.setFormatter(formatter)
 logger.addHandler(handler)
 
-
 def load_json(p):
     with open(p, 'r') as f:
         return json.loads(f.read())
@@ -100,13 +99,11 @@ class TreeWalker:
             for index, chapter in enumerate(level_node["children"]):
                 chapter_title = list(chapter.keys())[0]
                 chapter_node = list(chapter.values())[0]
-                chapter_path = os.path.join(
-                    level_path, f"{index+1}.{chapter_title}")
+                chapter_path = os.path.join(level_path, f"{index+1}.{chapter_title}")
                 self.load_sections(chapter_path, chapter_node)
                 for index, section_node in enumerate(chapter_node["children"]):
                     section_title = list(section_node.keys())[0]
-                    full_path = os.path.join(
-                        chapter_path, f"{index}.{section_title}")
+                    full_path = os.path.join(chapter_path, f"{index}.{section_title}")
                     if os.path.isdir(full_path):
                         self.ensure_exercises(full_path)
 
@@ -122,7 +119,8 @@ class TreeWalker:
             level_path = os.path.join(self.root, level)
             num, config = self.load_level_node(level_path)
             levels.append((num, config))
-        levels.sort(key=lambda item: item[0])
+
+        levels = self.resort_children(self.root, levels)
         root_node["children"] = [item[1] for item in levels]
         return root_node
 
@@ -148,7 +146,7 @@ class TreeWalker:
                 num, chapter = self.load_chapter_node(full_name)
                 chapters.append((num, chapter))
 
-        chapters.sort(key=lambda item: item[0])
+        chapters = self.resort_children(base, chapters)
         level_node["children"] = [item[1] for item in chapters]
         return level_node
 
@@ -160,10 +158,21 @@ class TreeWalker:
                 num, section = self.load_section_node(full_name)
                 sections.append((num, section))
 
-        sections.sort(key=lambda item: item[0])
+        sections = self.resort_children(base, sections)
         chapter_node["children"] = [item[1] for item in sections]
         return chapter_node
 
+    def resort_children(self, base, children):
+        children.sort(key=lambda item: item[0])
+        for index, [number, element] in enumerate(children):
+            title = list(element.keys())[0]
+            origin = os.path.join(base, f"{number}.{title}")
+            posted = os.path.join(base, f"{index+1}.{title}")
+            if origin != posted:
+                self.logger.info(f"rename [{origin}] to [{posted}]")
+            os.rename(origin, posted)
+        return children
+
     def ensure_chapters(self):
         for subdir in os.listdir(self.root):
             self.ensure_level_config(subdir)
@@ -220,8 +229,8 @@ class TreeWalker:
             config = {
                 "node_id": self.gen_node_id(),
                 "keywords": [],
-                "children": [],
-                "export": []
+                "children":[],
+                "export":[]
             }
             dump_json(config_path, config, exist_ok=True, override=True)
         else:
@@ -285,3 +294,4 @@ class TreeWalker:
             if "exercise_id" not in exercise:
                 exercise["exercise_id"] = uuid.uuid4().hex
                 dump_json(full_name, exercise)
+