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