The purpose of the task is to implement a function that will accept a single input parameter N and output a string with an ASCII art of the japanese flag.

Here is an example of flags for various values of N:

N = 2                           N = 6
########                        ####################
#      #                        #                  #
#  **  #                        #                  #
#  **  #                        #                  #
#      #                        #        **        #
########                        #       *oo*       #
                                #      *oooo*      #
N = 4                           #      *oooo*      #
##############                  #       *oo*       #
#            #                  #        **        #
#            #                  #                  #
#     **     #                  #                  #
#    *oo*    #                  #                  #
#    *oo*    #                  ####################
#     **     #
#            #
#            #
##############

The following is a list of requirements for the function:

• The input N shall be an integer even number
• The width of the inner area of the rectangle (excluding border) shall be 3 * N
• The height of the inner area of the rectangle (excluding border) shall be 2 * N
• The vertical distance between the circle and the border of the rectangle shall be N/2
• The horizontal distance between the circle and the border of the rectangle shall be N
• # symbol shall be used for rectangle border, * symbol shall be used for the circle border, o symbol shall be used for inner circle area
• The function shall return a string and use \n as line separators
• The function shall accept a single parameter N
• If the parameter is not a valid even integer number the ArgumentError exception shall be thrown
• The result of the task shall be provided a single python file named flag.py with a function named flag defined in it