- ➊ Write a number between 1 and N (=size of the diagram) into each white cell
- ➋ so that no number occurs more than once in a row or column (regardless of the color of the cell).
- ➌ The numbers in a horizontal or vertical stripe of consecutive white cells must form a sequence of numbers without gaps, but not necessarily in order (e.g. 2-3-4 or 5-4-7-6).