boolean found = false;
public TreeNode helper(TreeNode root, TreeNode p, TreeNode q)
{
    if(found||root==null) return null;
    TreeNode left = helper(root.left, p, q);
    TreeNode right = helper(root.right, p, q);

    if(left!=null&&right!=null)
    {
        found = true;
        return root;
    }
    if(root.val==p.val||root.val==q.val)
        return root;
    else if(left!=null)
        return left;
    else if(right!=null)
        return right;

    return null;
}