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Learning Opportunities

This puzzle can be solved using the following concepts. Practice using these concepts and improve your skills.

Statement

 Goal

The Ulam spiral or prime spiral is a graphical depiction of the set of prime numbers. It is constructed by writing the positive integers in a square spiral and specially marking the prime numbers.

You have to draw an Ascii representation of a Ulam spiral of size N×N.
Use '#' for prime numbers.
Use ' ' for others.

Example with N = 3 :
There are positions for the 3×3 Ulam spiral
5 4 3
6 1 2
7 8 9

Start at the center and turn counterclockwise

Then replace prime numbers with '#' and the others with ' ' :
#   #
#
#
Input
Line 1: An integer N for the size of the spiral
Output
N lines: Space separated characters of a line from the Ascii representation of the spiral (don't delete trailing ' ')
Constraints
N is odd
1 ≤ N ≤ 21
Example
Input
3
Output
#   #
    #
#    

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