<s>[INST] # Problem
Given a binary tree, find the lowest common ancestor (LCA) of two given nodes. The lowest common ancestor is defined between two nodes p and q as the lowest node in T that has both p and q as descendants (where the definition of "lowest" common ancestor takes into account that a node more towards the root is lower than one closer to the leaf).

**First Attempt:**
```python
class TreeNode:
    def __init__(self, x):
        self.val = x
        self.left = None
        self.right = None

def lowestCommonAncestor(root, p, q):
    if not root:
        return None
    if root == p or root == q:
        return root
    left = lowestCommonAncestor(root.left, p, q)
    right = lowestCommonAncestor(root.right, p, q)
    if left and right:
        return root
    return left or right  # This line is incorrect
```
The proposed solution has a bug. Can you identify the bug and provide a debugged version of the code?[/INST]