
0 0 0  4 0 0  0 0 0
1 0 0  0 0 0  0 0 0
5 9 0  0 0 0  3 0 0

6 0 7  0 0 5  0 0 0
3 0 5  0 4 0  2 0 8
0 0 0  8 0 0  7 0 1

0 0 1  0 0 0  0 8 6
0 0 0  0 0 0  0 0 2
0 0 0  0 0 4  0 0 0

challenge 18sep23
shows need of dig-triples on diag but within box
after much reduction kcell shows 2@11 is impossible since =>
3@22 7@91 9@99 => no 7@19 and no 9@19 => 19 empty
