Shortest path length:4
21-17-15-12-10
21-18-15-12-10
21-17-15-13-10
21-18-15-13-10
21-17-15-14-10
21-18-15-14-10
21-17-16-14-10
21-18-16-14-10
21-19-16-14-10
21-20-16-14-10