import collections
def main():
	double()

def double():
	n, a = [input() for _ in range(2)]
	a = a.split()
	a_new = collections.Counter(a)
	count = 0
	for i in a_new.values():
		if i > 1:
			count += i // 2
	print(count)

if __name__ == '__main__':
	main()