diff --git a/trees/bt_construct_inorder_preorder.py b/trees/bt_construct_inorder_preorder.py
index a6faa89..9087fe5 100644
--- a/trees/bt_construct_inorder_preorder.py
+++ b/trees/bt_construct_inorder_preorder.py
@@ -3,15 +3,16 @@
 # author: bt3gl
 
 
-def build_tree(preorder, inorder) -> Optional[Node]:
+def build_tree(preorder, inorder):
         
         def helper(left, right, index_map):
             
             if left > right:
                 return None
-            
-            root = Node(preorder.pop(0)) # # this order change from postorder
-            index_here = index_map[root.val]
+                    
+            node = preorder.pop(0) # this order change from postorder
+            root = Node(node.val) 
+            index_here = index_map[node.val]
 
             root.left = helper(left, index_here - 1, index_map) # this order change from postorder
             root.right = helper(index_here + 1, right, index_map)