13 6
-1 -1 -1 0 0 0 0
-1 -1 0 -1 0 0 0
-1 0 -1 -1 0 0 0
-1 0 0 0 -1 -1 0
-1 0 0 0 -1 0 -1
-1 0 0 0 0 -1 -1
-1 0 0 -1 -1 0 0
1 1 0 0 0 0 0
1 0 1 0 0 0 0
1 0 0 1 0 0 0
1 0 0 0 1 0 0
1 0 0 0 0 1 0 
1 0 0 0 0 0 1
0 -1 -1 -1 -1 -1 -1


# Corresponding graph:
#  +-----[b]    [e]-----+
#  |      |      |      |
# [a]----[c]----[d]----[f]

