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

Difficulty: Very hard (0)

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

Difficulty: Very easy (0)

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

Difficulty: Very easy (0)

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

Difficulty: Very easy (0)