def main():
	double()

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

if __name__ == '__main__':
	main()