Place each digit 1–7 exactly once in each row and column of the 7×7 grid. The grid is covered by 16 jigsaw pieces. Each piece covers the same sum. If a cell is covered by more than one piece, its digit is split between those pieces proportionally to the area covered. Eg if R4C4 contains the digit x, then this cell contributes ¼·x to the sum of the piece covering R3C3, ½·x to the sum of the piece covering R3C5, and ¼·x to the sum of the piece covering R5C5.