3
1	x	x	x	x	7	x	9	x
x	3	x	x	2	x	x	x	8
x	x	9	6	x	x	5	x	x
x	x	5	3	x	x	9	x	x
x	1	x	x	8	x	x	x	2
6	x	x	x	x	4	x	x	x
3	x	x	x	x	x	x	1	x
x	4	x	x	x	x	x	x	7
x	x	7	x	x	x	3	x	x