Each row, column, and region must contain the digits from 1 to 9 exactly once. The regions must be orthogonally connected and determined by the solver. Clues outside the grid show the sum of the two digits separated by the first region border seen from that direction in that row/column. (A row or column with a clue cannot be occupied by a single region.) For example; if the regions were the regular 3x3 boxes, then the clue at the top of column 6 would be the sum of R3C6 and R4C6, and the clue at the bottom of column 6 would be the sum of R6C6 and R7C6.