# -*- coding:utf-8 -*-
import collections

if __name__ == "__main__":
	n = input()
	items = []
	for i in xrange(n):
		items += map(int,raw_input().split())
	count = collections.Counter(items)
	ans = 0
	amari = 0
	for item, cnt in count.most_common():
		ans += cnt //2
		amari += cnt % 2
	ans += amari //4
	print ans