[QUIZ] Verbal Arithmetic (#128)

[Andreas Launila]

Since we now have to start exploring the search space we make a guess
that e=4. Propagating the constraints once again with e given the domain
4 will directly result in a failure, so we backtrack and now know that
e!=4. With that information we redo the propagation and directly end up
at the solution with no need to explore any further.

I forgot a node in the middle there (since there are 4 nodes). The
complete search is:

1) Root: s=9, e=4..7, n=5..8, d=2..8, m=1, o=0, r=2..8, y=2..8
2) Tries e = 4: fails.
3) Knows e != 4: s=9, e=5..7, n=6..8, d=2..8, m=1, o=0, r=2..8, y=2..8
4) Tries e = 5: s=9, e=5, n=6, d=7, m=1, o=0, r=8, y=2 (success)