There is a long-lived fly fluttering somewhere out there. Some say this fly is able to perform additions and substractions. Quite an amazing diptera, right?

Well, there are 7 friends who would disagree with us. During their 4 chess games, this house-fly would land (randomly, they thought) on some very specific chess squares. Games are enumerated from 1 (first) to 4 (last):


Now it is thought this diptera is smarter than suspected. It is following a pattern! You need to help these friends guess in what square it is going to land next, so they can finally put an end to its cockiness - swatting it hard!

Rolled newspapers ready; this is the game:


Can you help them identify the square the fly will touch down next?


This fly knows the time.


This fly knows the name of each and every one of the 7 players.


This fly has a curious habit: it lands on the board only after one of the players surrenders. Some calculations after that, the diptera chooses the square.


Mind the 'Knowledge' tag.

  • 2
    $\begingroup$ I think the fly will move to the 6th rank because it moves up or down the same number of squares as the black king each game. I have not figured out the pattern about moving from right to left. Game 2 the black king moves up two ranks so does the fly. Game 3 the black king stays on the same rank and so does the fly. Game 4 the black king moves down 4 ranks and so does the fly (falling off the bottom of the board and landing on the top). So game 5 the fly will move down 1 square just like the black king $\endgroup$
    – Jeff
    Commented Jun 6, 2016 at 2:18
  • $\begingroup$ I can't decipher your clue "the fly knows the time" I tried looking at the fly and various pieces as hands on a clock but can't quite see the right to left pattern yet. The fly does not seem to move like a regular chess piece when leaving one game and landing on the next. $\endgroup$
    – Jeff
    Commented Jun 6, 2016 at 2:27
  • $\begingroup$ Either this is a very small chess board, or a damn big and ugly fly. ;c) $\endgroup$
    – BmyGuest
    Commented Jun 6, 2016 at 6:48
  • 1
    $\begingroup$ It's a damn big, ugly and smart fly!! Haha $\endgroup$ Commented Jun 6, 2016 at 13:39
  • 3
    $\begingroup$ Speculation for any chess gurus to consider: The hints and the reference to 7 unnames players leads me to believe the board states represented above are from 4 well known games between 7 known chess players. Perhaps the fly (if it really is smart) is predicting the next move(s) of one of the players or predicting the spot that the king will be checkmated in or something along those lines. I could be way off but just food for thought $\endgroup$
    – NeedAName
    Commented Jun 6, 2016 at 14:19

3 Answers 3


I think the fly will land on square


It seems the informations the fly uses are

the name of the winner, the color he played and the year in which the game took place.

It determines the square on which it lands in the following way:

If White won, take the first letter of his first name. If Black won, take the first letter of his last name. Then sum the digits of the year, and take the rest of the division by 8 (if the rest is 0, take 8). The letter and number obtained are the coordinates of the square.

The invaluable answer by Mark Peters allows us to check this pattern in the four first games.

Thus, in the first game,

Robert J. Fischer won, playing Black, in 1970. This gives f1.

In the second game,

Garry Kasparov won, playing White, in 1990. This gives g3.

In the third game,

Alexander Grischuk won, playing White, in 2001. This gives a3.

Finally, in the fourth game,

Alexander Grischuk won again, this time playing Black, in 2005. This gives g7.

Therefore, for the current game,

Alexander Grischuk won yet again, playing Black, in 2007. This gives g1.

Board solution:


  • $\begingroup$ Correct! Half credit for you, half for @MarkPeters. Good job guys! $\endgroup$ Commented Jun 7, 2016 at 16:34
  • $\begingroup$ That fly was totally squashed by @MarkPeters' knowledge drop. $\endgroup$
    – quidam
    Commented Jun 7, 2016 at 16:37
  • $\begingroup$ @quidam: Wow and I almost didn't include the year because I didn't think it would be relevant. Awesome job! $\endgroup$ Commented Jun 7, 2016 at 21:53
  • $\begingroup$ That is a pretty sweet solution. Kudos to @JoseLopez for the puzzle and of course to quidam for the solution. How many different things did you try before you discovered the correct algorithm? $\endgroup$
    – NeedAName
    Commented Jun 8, 2016 at 15:10

Not an answer, but I'm contributing the "Knowledge":

Game 1:

Tal vs Fischer, 1970
White to play.

Game 2:

Kasparov vs Karpov, 1990
Black to play

Game 3:

Grischuk vs Bareev, 2001
Black to play

Game 4:

Morozevich vs Grischuk, 2005
White to play

The seven players are therefore:

Tal, Fischer, Kasparov, Karpov, Grischuk (x2), Bareev, and Morozevich.

The current game is:

Carlsen vs Grischuk, 2007
White to play

  • $\begingroup$ Great job, +1 !! The puzzle now continues. $\endgroup$ Commented Jun 7, 2016 at 15:14
  • $\begingroup$ Is there a particular tool you used to get this info? $\endgroup$
    – NeedAName
    Commented Jun 7, 2016 at 15:20
  • 1
    $\begingroup$ @NeedAName: Yep, I used the lichess editor to obtain the FEN (a text representation of the board). Then I imported it (using the clipboard icon) in ChessTempo's game database and clicked the "Games for Position" tab to search games in their free database. Note that the castling state and whose turn it is are both part of the FEN, so you need to fiddle with those to find the matching games (in the case of these 5 games it's obvious that neither player can castle so only white/black to play matters). $\endgroup$ Commented Jun 7, 2016 at 15:22
  • $\begingroup$ Dat knowledge drop! Thanks for the info and links $\endgroup$
    – NeedAName
    Commented Jun 7, 2016 at 15:28
  • $\begingroup$ Are all of the games actually over? Did they all resign at this point? $\endgroup$
    – LeppyR64
    Commented Jun 7, 2016 at 15:35

Very partial answer

It could be related to "resigning in time" (giving up in a subtle way by intentionally letting the clock running out of time) :
- Fits with "This fly knows the time."
- Fits with "it lands on the board only after one of the players surrenders".

My theory for the moment would be that the fly knows when someone is currently resigning in time (so their clock isn't at 00:00 yet). So, that means no player will move or touch any piece until the clock runs out of time, so it can come safely on the board.

However, I don't figure out the logic in its positioning yet (maybe related to the time displayed on the clock ?).

  • $\begingroup$ Mind the Knowledge tag, @Menace! $\endgroup$ Commented Jun 7, 2016 at 12:39
  • $\begingroup$ The tag description is "A puzzle whose solution relies on external sources (like tables, dictionaries, wikipedia).", I don't understand what it really means. I mean, I had to search on the internet to find the "resigning in time" technique and I think many people not knowing much about chess like me wouldn't know it neither. So I thought it would have fit the tag, but apparently not :( $\endgroup$
    – Mayo
    Commented Jun 7, 2016 at 12:43
  • $\begingroup$ What else can you look for somewhere in Google in this Puzzle? $\endgroup$ Commented Jun 7, 2016 at 12:47

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