This little puzzle may be solved in as few as nine moves. Play the
engines as follows: From 9 to 10, from 6 to 9, from 5 to 6, from 2 to 5,
from 1 to 2, from 7 to 1, from 8 to 7, from 9 to 8, and from 10 to 9.
You will then have engines A, B, and C on each of the three circles and
on each of the three straight lines. This is the shortest solution that
is possible.