There are N cities numbered from 1 to N. You are given connections, where each connections[i] = [city1, city2, cost] represents the cost to connect city1 and city2 together. (A connection is bidirectional: connecting city1 and city2 is the same as connecting city2 and city1.) Return the minimum cost so that for every pair of cities, there exists a path of connections (possibly of length 1) that connects those two cities together. The cost is the sum of the connection costs used. If the task is impossible, return -1. Example 1: Input: N = 3, connections = [[1,2,5],[1,3,6],[2,3,1]] Output: 6 Explanation: Choosing any 2 edges will connect all cities so we choose the minimum 2. Example 2: Input: N = 4, connections = [[1,2,3],[3,4,4]] Output: -1 Explanation: There is no way to connect all cities even if all edges are used. Note: 1 <= N <= 10000 1 <= connections.length <= 10000 1 <= connections[i][0], connections[i][1] <= N 0 <= connections[i][2] <= 10^5 connections[i][0] != connections[i][1]