Definition: A subset of cells is a 8-loop if entries of +8 and -8 are put alternately in the cells of the loop, such that if a row or a column contains a cell from the loop with a +8 entry, then it also contains an entry with a-8.
Definition: A subset of cells is a 8-loop if entries of +8 and -8 are put alternately in thecells of the loop, such that if a row or a column contains a cell from the loop with a +8entry, then it also contains an entry with a-8.