Depth-first search

Apply the DFS procedure for the following undirected graph:

Start the algorithm with the node $4$. If there are several nodes to choose to process next, pick the one with the smallest label.

Print the resulting spanning tree for the graph in the following format:

1 -> 2
2 -> 3
3 -> 4
4 -> 5

Here, each line represents an edge. In your output, the edges should be printed in the order of traversal.