8
4
2
2
5
3
2
5
9
8
1
4
5
9
6
6
8
5
1
7
2
7
2
9
3
7
9
8
7
6
2
1
9
5
4
8
"Chess demands total concentration." — Bobby Fischer
"Chess demands total concentration." — Bobby Fischer
When a box has only two empty cells, you know exactly which two digits fill them.
When a box has only two empty cells, you know exactly which two digits fill them.