

'''simple docstring'''



from math import factorial







def    a__       (  a__ = 20						):




     """simple docstring"""


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

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


if __name__ == "__main__":
  import sys

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










from __future__ import annotations


def        _UpperCamelCase							(      lowercase__      ):
						__SCREAMING_SNAKE_CASE						:     Dict					=		0.00
						__SCREAMING_SNAKE_CASE						:     List[str]					=		0
						for resistor in resistors:
												if resistor <= 0:
																		__SCREAMING_SNAKE_CASE						:     Any					=		F'''Resistor at index {index} has a negative or zero value!'''
																		raise ValueError(lowercase__      )
												first_sum += 1 / float(lowercase__      )
												index += 1
						return 1 / first_sum


def        _UpperCamelCase							(      lowercase__      ):
						__SCREAMING_SNAKE_CASE						:     Tuple					=		0.00
						__SCREAMING_SNAKE_CASE						:     int					=		0
						for resistor in resistors:
												sum_r += resistor
												if resistor < 0:
																		__SCREAMING_SNAKE_CASE						:     Tuple					=		F'''Resistor at index {index} has a negative value!'''
																		raise ValueError(lowercase__      )
												index += 1
						return sum_r


if __name__ == "__main__":
						import doctest

						doctest.testmod()
