

from collections import Counter


def 			_UpperCAmelCase							(		a__):

			'''simple docstring'''



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


if __name__ == "__main__":
	import doctest

	doctest.testmod()

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





def 			_UpperCAmelCase							(		a__):

			'''simple docstring'''



			return 1 if input_a == 0 else 0


def 			_UpperCAmelCase							(		):

			'''simple docstring'''



			assert not_gate(0) == 1
			assert not_gate(1) == 0


if __name__ == "__main__":
	print(not_gate(0))
	print(not_gate(1))


