Chess: checkmate in four and a single line of play — can you crack it?

China’s Ding Liren is the favourite to challenge for Magnus Carlsen’s world title in 2020, but this week the 26-year-old from Wenzhou faces a massive dilemma as the $1.6m 128-player World Cup knock-out in Siberia reaches its semi-finals.

The pairings are Ding Liren (China) v Yu Yangyi (China) and Maxime Vachier-Lagrave (France) v Teimour Radjabov (Azerbaijan). Normal expectation would be for Ding and Vachier-Lagrave to meet in the final after defeating their lower ranked opponents, but there is a seriously complicating factor.

Both finalists will qualify among the eight candidates who will play in 2020 for the right to be Carlsen’s challenger later next year. Ding is also virtually assured of a qualification spot by virtue of his high international rating, but if he has a double qualification the World Cup route takes preference.

So Ding’s dilemma is also an opportunity. The candidates venue is Ekaterinburg, the former Sverdlovsk. Two top Russians may qualify by another route, and the organisers also have a wildcard place, which could mean three Russians in the field of eight. But if Yu beats Ding this week, there will also be two Chinese players.

The games themselves are online Thursday and Friday (tiebreaks Saturday if needed) starting 11am BST, and will reveal how Ding resolves his dilemma.

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White forces checkmate in four moves,with just a single line of play (by Fritz Giegold,1957). The puzzle challenge sounds easy, but the answer is well hidden.

Click here for solution