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RULES

1 Each row and each column must contain the numbers 1 through 4 (easy) or 1 through 6 (challenging) without repeating.

2 The numbers within the heavily outlined boxes, called cages, must combine using the given operation (in any order) to produce the target numbers in the top-left corners.

3 Freebies: Fill in single-box cages with the number in the top-left corner.