import math

N = int(input())

items = []
for i in range(N):
	items += list(map(int, input().split()))

items_uniq = list(set(items))

n = 0
m = 0
d = dict([(i, 0) for i in items_uniq])
for i in range(N * 3):
	if d[items[i]] == 1:
		d[items[i]] = 0
		n -= 1
		m += 1
	else:
		d[items[i]] = 1
		n += 1

print(m + math.floor(n / 4))