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

Difficulty: Very easy (0)

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

Difficulty: Very easy (0)

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

Difficulty: Very easy (0)

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

Difficulty: Very hard (0)