public class Graph
{
  private final int V; // number of vertices
  private int E; // number of edges
  private Bag<Integer>[] adj; // adjacency lists
  public Graph(int V)
  {
    this.V = V; this.E = 0;
    adj = (Bag<Integer>[]) new Bag[V]; // Create array of lists.
    for (int v = 0; v < V; v++) // Initialize all lists
      adj[v] = new Bag<Integer>(); // to empty.
  }
  public Graph(In in)
  {
    this(in.readInt()); // Read V and construct this graph.
    int E = in.readInt(); // Read E.
    for (int i = 0; i < E; i++)
      { // Add an edge.
        int v = in.readInt(); // Read a vertex,
        int w = in.readInt(); // read another vertex,
        addEdge(v, w); // and add edge connecting them.
      }
  }
  public int V() { return V; }
  public int E() { return E; }
  public void addEdge(int v, int w)
  {
    adj[v].add(w); // Add w to vb    <pre></pre>s list.
    adj[w].add(v); // Add v to wb    <pre></pre>s list.
    E++;
  }
  public Iterable<Integer> adj(int v)
  { return adj[v]; }
}