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

Difficulty: Easy (0)

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

Difficulty: Very easy (0)

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

Difficulty: Very easy (0)

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

Difficulty: Very easy (0)