The St. Petersburg event was arranged in an unusual way : after a preliminary single-round all-play-all tournament of eleven players , the top five were to play a second stage in a double round format , with scores from the preliminary tournament carried forward to the second contest . This event was arranged in an unusual way : after a preliminary single round-robin tournament involving 11 players , the top five were to play a second stage in double round-robin format , with scores from the preliminary tournament carried forward to the second contest .