N = input()
items = {}
for i in range(N):
	a = map(int,raw_input().split())
	for aa in a:
		if items.has_key(aa):
			items[aa] += 1
		else:
			items[aa] = 1
upCount = 0
count = 0
for key in items.keys():
	if items[key] == 1:
		count += 1
	upCount += int(items[key] / 2)
if count >= 4:
	upCount += int(count /4)
print upCount