I thank Christoph Bandelow for allowing this chess problem, with a mathematical flavor, to be posted here.

**Position:**

- In algebraic:White: King g8, Queen e2, Bishops a1 and g4, Pawn e6 (5 pieces),Black: King f6, Bishop a2, Knight b1 (3 pieces).
- In Forsyth notation:
6K1 8 4Pk2 8 6B1 8 b3Q3 Bn6

**What were the last 6 single moves? (retrochess problem by Christoph Bandelow) **

Solution: -1. d5xe6 e.p.+ -2. ….. e7-e5 -3. d4-d5+ -4. ….. Ke6xPf6+ -5. e5xf6 e.p.++ -6. ….. f7-f5

Shouldn’t the solution be -1. d5xe6 e.p.+ -2. ….. e7-e5 -3. d4-d5+ -4. ….. Ke6xPf6 -5. e5xf6 e.p.++ -6. ….. f7-f5

Sorry for the late reply. Yes, you are correct. It’s fixed now. Thanks!

I recently discovered this problem in a book of mathematics.

As of right now (I’m open to being convinced otherwise), I’m convinced there is no legal previous move (-1).

There was a typo in the solution. It’s fixed now. Thanks!