<s>[INST] A binary tree is said to be "correct" if the following conditions are met:

* The left subtree of a node should only have keys less than the node's key.
* The right subtree of a node should only have keys greater than the node's key.
* For any node, all elements in the left subtree and right subtree must also follow the above rules.

Here's an example of a correct binary tree:
       4
      / \
     2   6
    / \   \
   1   3   5

Given a binary tree, you need to find the maximum depth of a correct subtree. You might need to exclude some nodes.

For example:
      5
     / \
    3   7
   / \   \
  2   4   8

The maximum depth of a correct subtree is 2.

You can use a helper function to get the depth of a correct BST in the given subtree, given the minimum and maximum values.
Here's the code:
```python
def maxDepth(root):
    def isCorrectBST(node, min_val, max_val):
        if not node:
            return True

        if node.val <= min_val or node.val >= max_val:
            return False

        return isCorrectBST(node.left, min_val, node.val) and isCorrectBST(node.right, node.val, max_val)

    def getDepth(node, min_val, max_val):
        if not isCorrectBST(node, min_val, max_val):
            return 0

        left_depth = getDepth(node.left, min_val, node.val)
        right_depth = getDepth(node.right, node.val, max_val)

        return max(left_depth, right_depth) + 1

    if root:
        return getDepth(root, float('-inf'), float('inf'))
    else:
        return 0
```
However, the current solution assumes all keys in the tree are distinct. If the keys are not distinct, the current code will return an incorrect result. How can you modify the solution to handle duplicate keys?[/INST]