There are n servers numbered from 0 to n-1 connected by undirected server-to-server connections forming a network where connections[i] = [a, b] represents a connection between servers a and b. Any server can reach any other server directly or indirectly through the network. A critical connection is a connection that, if removed, will make some server unable to reach some other server. Return all critical connections in the network in any order. Example 1: Input: n = 4, connections = [[0,1],[1,2],[2,0],[1,3]] Output: [[1,3]] Explanation: [[3,1]] is also accepted. Constraints: 1 <= n <= 10^5 n-1 <= connections.length <= 10^5 connections[i][0] != connections[i][1] There are no repeated connections.