






"""simple docstring"""





from collections import Counter






def 							A(    snake_case_						):
       """simple docstring"""





       return sum(socks_by_color // 2 for socks_by_color in Counter(snake_case_						).values()						)


if __name__ == "__main__":
  import doctest

  doctest.testmod()

  UpperCamelCase					=     [int(x) for x in input("""Enter socks by color :""").rstrip().split()]
  print(F"sock_merchant({colors}) = {sock_merchant(colors)}")








"""simple docstring"""







def        __lowerCAmelCase							(_UpperCamelCase = 10**6						):

	if n <= 0:
		raise ValueError('Please enter an integer greater than 0'						)

	__lowerCAmelCase     :		Optional[Any]		     = list(range(n + 1						)						)
	for number in range(2			,    n + 1						):
		if phi[number] == number:
			phi[number] -= 1
			for multiple in range(number * 2			,    n + 1			,    _UpperCamelCase						):
				__lowerCAmelCase     :		Tuple		     = (phi[multiple] // number) * (number - 1)

	__lowerCAmelCase     :		Any		     = 1
	for number in range(1			,    n + 1						):
		if (answer / phi[answer]) < (number / phi[number]):
			__lowerCAmelCase     :		List[Any]		     = number

	return answer


if __name__ == "__main__":
							print(solution())