You are given a list of directed edges `edges`, where each edge is represented as `[parent, child]`. The graph contains nodes labeled from `1` to `n`, and it was originally a rooted tree with exactly one extra directed edge added. A valid rooted tree must satisfy all of the following: - Exactly one node is the root and has no parent. - Every other node has exactly one parent. - All nodes are reachable from the root. - There are no directed cycles. Your task is to return the single edge that should be removed so that the remaining edges form a valid rooted tree. If there are multiple candidate edges, return the one that appears last in the input. Example: - Input: `[[1,2],[1,3],[2,3]]` - Output: `[2,3]`