code: 
  
  """simple docstring"""
  
  
  
  
  def      __SCREAMING_SNAKE_CASE		(		lowercase__    ,							lowercase__    ,							lowercase__   ):
  					"""simple docstring"""
  
  					if power < 0:
  										return -1
  					base %= mod
  					A    =      1
  
  					while power > 0:
  										if power & 1:
  															A    =      (result * base) % mod
  										A    =      power >> 1
  										A    =      (base * base) % mod
  
  					return result
  def      __SCREAMING_SNAKE_CASE		(		):
  					"""simple docstring"""
  					print(modular_exponential(3    ,							200    ,							13   )   )
  
  
  if __name__ == "__main__":
  	import doctest
  
  	doctest.testmod()
  
  	main()
  
  
  
  
  
  
style_context: 
  
  """simple docstring"""
  
  
  
  
  def      __SCREAMING_SNAKE_CASE		(		lowercase__   ):
  					"""simple docstring"""
  					if not isinstance(lowercase__    ,							lowercase__   ):
  										raise ValueError("double_factorial() only accepts integral values"   )
  					if n < 0:
  										raise ValueError("double_factorial() not defined for negative values"   )
  					return 1 if n <= 1 else n * double_factorial(n - 2   )
  
  
  if __name__ == "__main__":
  	import doctest
  
  	doctest.testmod()
  
  
  
  
  
  