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

Difficulty: Very easy (0)

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

Difficulty: Easy (0)

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

Difficulty: 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)