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
ans = 0
for key in items.keys():
	if items[key] >= 2:
		ans += items[key] / 2 
		items[key] -= (items[key] / 2) * 2
		del items[key]
ans += len(items)/4
print ans