
from math import factorial




def 							a		(				snake_case__:   int = 20   ):


				'''simple docstring'''
				lowercase_	    =   2 * n  # middle entry of odd rows starting at row 3 is the solution for n = 1,
				# 2, 3,...
				lowercase_	    =   n // 2

				return int(factorial(snake_case__   ) / (factorial(snake_case__   ) * factorial(n - k   ))   )


if __name__ == "__main__":
						import sys

						if len(sys.argv) == 1:
												print(solution(2_0))
						else:
												try:
																		__a         =   int(sys.argv[1])
																		print(solution(n))
												except ValueError:
																		print('Invalid entry - please enter a number.')






def 							a		(				snake_case__:   int   ):


				'''simple docstring'''
				if not isinstance(snake_case__		,  snake_case__   ):
								raise ValueError('''Input must be an integer'''   )
				if input_num <= 0:
								raise ValueError('''Input must be positive'''   )
				return sum(
				    divisor for divisor in range(1		,  input_num // 2 + 1   ) if input_num % divisor == 0   )


if __name__ == "__main__":
						import doctest

						doctest.testmod()




