Print a Sqare Matrix in a Helical fashion.

Print a N*N square matrix in a helical way.
to illustrate:

1	->	2	->	3	->	4
						|
5	->	6	->	7		8
|				|		|
9		10	<-	11		12
|						|
13	<-	14	<-	15	<-	16

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