
from collections import Counter


def 					__lowerCAmelCase    (    a__						) ->						int:
				return sum(socks_by_color // 2 for socks_by_color in Counter(a__						).values()						)


if __name__ == "__main__":
					import doctest

					doctest.testmod()

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








from itertools import compress, repeat
from math import ceil, sqrt


def 					__lowerCAmelCase    (    a__						) ->						list[int]:

				if num <= 2:
								return []
				if num == 3:
								return [2]

				# Odd sieve for numbers in range [3, num - 1]
				__a    							=					bytearray(B'''\x01'''						) * ((num >> 1) - 1)

				for i in range(3		,					int(sqrt(a__						)						) + 1		,					2						):
								if sieve[(i >> 1) - 1]:
												__a    							=					i**2
												__a    							=					repeat(
												    0		,					ceil((num - i_squared) / (i << 1)						)						)

				return [2] + list(compress(range(3		,					a__		,					2						)		,					a__						)						)


if __name__ == "__main__":
					import doctest

					doctest.testmod()