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To celebrate the front page of the May issue of The Problemist, or perhaps the start
of the Giro d’Italia, this week’s problem turns to themes cyclic. All will be
revealed in the solution on Friday!

What we have here is an example of a cyclic Zagoruiko. In both the try- and
post-key phases, Black has two defences x and y. In one phase, they are refuted
respectively by mates A and B, in the next, by mates B and C, and in the third by
mates C and A.

Thus, after the first try 1.Qxd3? (threat 2.Qf3) the thematic defences 1...Sxe5 (X)
and 1...Sxd4 (Y) are met by the mates 2.Sc7# (A) and 2.Bxb7# (B), but the third
defence 1...Ra3! refutes.

A second try is 1.Qf5? (with the same threat). Now 1...Sxe5/1...Sxd4 run into the
mates 2.Bxb7(B) and 2.Sb6 (C), but 1...g4! refutes.

Finally, after the key 1.Bf8! Threat 2.Qh1, we have 1...Sxe5 2.Sb6# (C)
and 1...Sxd4 2.Sc7# (A)

So what we have is a 3x2 Zagoruiko (two changed mates in three phases of play),
with a cyclic pattern across the three phases, which can be summarised as
1. x-A y-B / 2.x-B y-C / 3.x-C y-A.

Any comments or questions on this problem should be addressed to
Steve Giddins (our Libarian and Archivist) using the 'Contact'
item in the menu on the left.