7
5
8
2
4
6
4
7
8
4
6
7
1
9
9
6
2
6
3
9
4
8
9
5
3
7
1
9
8
9
8
5
6
1
"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.