From WPC unofficial wiki


Enter numbers from 1 to X into the grid, so that each number appears exactly once in each row and column. Some grid points contain a clue consisting of a number and an arithmetic operator. The clue number must be the result of the given operator being applied to a pair of diagonally opposite adjacent cells, and it must be valid for both such pairs of cells. If a grid point is marked with an E (“even”) or O (“odd”), then all four adjacent cells must contain even respectively odd numbers.

(Rules (modified) and example from WPC 2019 IB)

History of the puzzle[edit]

Invented by Otto Janko (Austria) in 2010. [1]

Appearances in the past WPCs[edit]