import java.util.ArrayList;
import java.util.List;
import java.util.Set;

/**
 *
 * @author Oleg
 */
class DFS {

    /**
     * @param args the command line arguments
     */
    public static void main(String[] args) {

    }

    private static int length;

    public static int findWay(Graph g, Graph.Vertex start, Graph.Vertex end) {

        length = 0;
        List<Graph.Vertex> way = new ArrayList<Graph.Vertex>();
        way.add(start);
        nextStep(g,start,end,way);
        return --length;
    }

    private static void nextStep(Graph g, Graph.Vertex start, Graph.Vertex end, List<Graph.Vertex> way) {

        Set<Graph.Vertex> neighbors = g.getNeighbors(start);
        for(Graph.Vertex neighbor : neighbors) {
            if(way.contains(neighbor))
                continue;
            way.add(neighbor);
            if(neighbor.equals(end) && (length == 0 || length > way.size()))
                length = way.size();
            nextStep(g,neighbor,end,way);
            way.remove(way.size() - 1);
        }
    }
}