Masakuchi is a variation of Makaro puzzle published by Nikoli. A rectangular or square grid is divided into regions. Each region must be filled with each of the digits from 1 to the number of cells in the region. When two numbers are orthogonally adjacent across a region boundary, the numbers must be different. The grid may contain black cells with arrows and numbers: the arrow points at the greatest number among the four cells around (up, under, left, right) the black cell. The number in the black cell shows the difference between the greatest number and the second highest number in all orthogonally adjacent cells around the black cell.
Cross+A can solve puzzles from 3 x 3 to 30 x 30.