
0 0 2  0 0 0  0 0 0
0 0 0  5 0 0  4 0 0
0 0 5  0 0 7  0 0 0

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

0 0 0  8 0 0  2 0 0
0 0 9  0 0 6  0 0 0
0 0 0  0 0 0  1 0 0

xdad4 extreme 
needs many methods to solve
but KeyCell not needed
