Place tiles of 1x2 cells in the grid, with numbers 1 and 2 each. Tiles can be rotated but they cannot touch each other, even diagonally. Numbers outside the grid indicate the sum of all the numbers in the corresponding row/column.
(Rules and example from WPC 2012 IB)
History of the puzzle
First appeared on WPC 2012/Round 2 ("Blackjack", a 21-themed round) to commemorate the 21st World Puzzle Championship. Author of the puzzle is unknown.