class Solution {
    public TreeNode lowestCommonAncestor(TreeNode root, TreeNode p, TreeNode q) {
        if (root==null)
            return null;
        if (root.val==p.val || root.val==q.val)
            return root;
        TreeNode left=lowestCommonAncestor(root.left, p, q);
        TreeNode right=lowestCommonAncestor(root.right, p, q);
 
        if (left==null)
            return right;
        if (right==null)
            return left;
        return root;    
    }
}