from collections import Counter

    #inp
n=int(input())
items=[]
up=0

for _ in range(n):
    items+=input().split()

#exe
dic_items=Counter(items)

for (i,j) in dic_items.items():
    up+=j//2
    dic_items[i]=j%2

up+=sum(list(dic_items.values())) //4

print(up)