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

#偶数個あるアイテムでのパワーアップ
p_1 = [itm.count(i) // 2 for i in set(itm) if itm.count(i) % 2 == 0]
p_1s = sum(p_1)

#奇数個あるアイテムでのパワーアップ（1個は数えず）
p_2 = [itm.count(i) // 2 for i in set(itm) if itm.count(i) % 2 == 1 and itm.count(i) != 1]
p_2s = sum(p_2) 

#その他でのパワーアップ
p_3 = [itm.count(i) % 2 for i in set(itm) if itm.count(i) % 2 == 1 and itm.count(i) != 1]
p_3s = sum(p_3) 

p_4 = [itm.count(i) for i in set(itm) if itm.count(i)  == 1]
p_4s = sum(p_4)

p_5s = (p_3s + p_4s) // 4

#ans
print(p_1s + p_2s + p_5s)