Shortest Path in Weighted Directed Graph

Given a weighted directed graph, find the shortest path from a specified starting point to all nodes in the graph. Return the time required to traverse all nodes in the shortest path; return -1 if it is impossible to reach all nodes. Example Input 4 [(1, 2, 1), (2, 3, 1), (1, 3, 4), (3, 4, 2)] 1