import math

N = int(input())
li = []
match = 0
other = 0
for i in range(N):
    l = list(map(int, input().split()))
    li.extend(l)

li.sort()

while not len(li) == 0:
    head = li[0]
    count = li.count(li[0])
    match += count / 2
    other += count % 2
    while head in li:
        li.remove(head)

print(math.floor(match) + math.floor((other / 4)))