One bad move nullifies forty good ones.
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[Event "rated untimed match"]
[Site "?"]
[Date "????.??.??"]
[Round "?"]
[White "White player"]
[Black "Black player"]
[Result "*"]
[BlackElo "0"]
[FEN "7K/8/1Q6/8/4k3/8/8/8 w - - 0 1"]
[SetUp "1"]
[TimeControl "0"]
[WhiteElo "0"]
{ Finish It! } 1. Kg7 { Any of a number of moves are also good, such as 1. Qd6. } 1... Kd5 2. Qb4 { Again, any number of moves are also good, such as 2. Kf6. } 2... Ke5 3. Qc4 Kf5 4. Qd4 Ke6 5. Kg6 Ke7 6. Qd5 Ke8 7. Kf6 Kf8 8. Qd8# { Or Qf7#. } *