An edge in an undirected connected graph is a bridge if removing it disconnects the graph. 
Given a graph with node from 1 to n, and a list of integer pairs represent edges, return all the bridges. 

Example: 
n = 4
edges = [[1, 2], [1, 3], [1, 4]]

Output: 
[[1, 2], [1, 3], [1, 4]]

Explanation:
If any of the edges removed, the graph will be disconnected. 

Example2: 
n = 4
edges = [[1, 2], [1, 3], [2, 3]]

Output: 
[]

Explanation:
No bridges.