code: 
  
  from __future__ import annotations
  
  class __UpperCamelCase    :
  
  
  
  
  
  
  					'''simple docstring'''
  
  
  
  					def __init__(							self							,			lowerCamelCase__	):
  						UpperCAmelCase__:  Any		       =   data
  						UpperCAmelCase__:  List[Any]		       =   None
  
  class __UpperCamelCase    :
  
  
  
  
  
  
  					'''simple docstring'''
  
  
  
  					def __init__(							self	):
  						UpperCAmelCase__:  Any		       =   None
  
  
  
  
  
  					def       _UpperCAmelCase						(							self							,			lowerCamelCase__	):
  						UpperCAmelCase__:  Dict		       =   Node(lowerCamelCase__	)
  						UpperCAmelCase__:  Tuple		       =   self.head
  						UpperCAmelCase__:  Tuple		       =   new_node
  						return self.head.data
  
  
  
  
  
  					def       _UpperCAmelCase						(							self	):
  						UpperCAmelCase__:  Optional[Any]		       =   self.head
  						UpperCAmelCase__:  Tuple		       =   self.head
  						if self.head:
  							while fast_pointer and fast_pointer.next:
  								UpperCAmelCase__:  str		       =   fast_pointer.next.next
  								UpperCAmelCase__:  List[str]		       =   slow_pointer.next
  							return slow_pointer.data
  						else:
  							print("No element found."	)
  							return None
  
  
  if __name__ == "__main__":
  					_lowerCAmelCase     :			List[Any]    =LinkedList()
  					for _ in range(int(input().strip())):
  										_lowerCAmelCase     :			List[Any]    =int(input().strip())
  										link.push(data)
  					print(link.middle_element())
style_context: 
  
  from __future__ import annotations
  
  from collections import Counter
  
  
  
  def  _A  (			SCREAMING_SNAKE_CASE			):
  	UpperCAmelCase__:  Optional[Any]		       =   [True] * n
  	UpperCAmelCase__:  Any		       =   False
  	UpperCAmelCase__:  Tuple		       =   False
  	UpperCAmelCase__:  Optional[Any]		       =   True
  
  	for i in range(3  ,int(n**0.5 + 1			)  ,2			):
  		UpperCAmelCase__:  Any		       =   i * 2
  		while index < n:
  			UpperCAmelCase__:  Optional[int]		       =   False
  			UpperCAmelCase__:  Tuple		       =   index + i
  
  	UpperCAmelCase__:  int		       =   [2]
  
  	for i in range(3  ,SCREAMING_SNAKE_CASE  ,2			):
  		if is_prime[i]:
  			primes.append(SCREAMING_SNAKE_CASE			)
  
  	return primes
  
  
  
  def  _A  (			SCREAMING_SNAKE_CASE			):
  	UpperCAmelCase__:  List[Any]		       =   str(SCREAMING_SNAKE_CASE			)
  	UpperCAmelCase__:  Tuple		       =   []
  	UpperCAmelCase__:  Optional[int]		       =   ["0", "1", "2", "3", "4", "5", "6", "7", "8", "9"]
  
  	for duplicate in Counter(SCREAMING_SNAKE_CASE			) - Counter(set(SCREAMING_SNAKE_CASE			)			):
  		UpperCAmelCase__:  Optional[Any]		       =   [int(number_str.replace(SCREAMING_SNAKE_CASE  ,SCREAMING_SNAKE_CASE			)			) for digit in digits]
  		replacements.append(SCREAMING_SNAKE_CASE			)
  
  	return replacements
  
  
  
  def  _A  (			SCREAMING_SNAKE_CASE = 8			):
  	UpperCAmelCase__:  Union[str, Any]		       =   set()
  
  	# Filter primes with less than 3 replaceable digits
  	UpperCAmelCase__:  Optional[Any]		       =   {
  	    x for x in set(prime_sieve(1_0_0_0_0_0_0			)			) if len(str(SCREAMING_SNAKE_CASE			)			) - len(set(str(SCREAMING_SNAKE_CASE			)			)			) >= 3
  	}
  
  	for prime in primes:
  		if prime in numbers_checked:
  			continue
  
  		UpperCAmelCase__:  Optional[int]		       =   digit_replacements(SCREAMING_SNAKE_CASE			)
  
  		for family in replacements:
  			numbers_checked.update(SCREAMING_SNAKE_CASE			)
  			UpperCAmelCase__:  Dict		       =   primes.intersection(SCREAMING_SNAKE_CASE			)
  
  			if len(SCREAMING_SNAKE_CASE			) != family_length:
  				continue
  
  			return min(SCREAMING_SNAKE_CASE			)
  
  	return -1
  
  
  if __name__ == "__main__":
  					print(solution())