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

Difficulty: Very easy (0)

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

Difficulty: Easy (0)

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

Difficulty: Very hard (0)

		1						5
						8
					9
			4		3		2
	3		9		2		1
	4		1		8
			2
		2
3						5

Difficulty: Very easy (0)