#!/usr/bin/python
from collections import Counter 
from itertools import chain
flatten = lambda listOfLists: chain.from_iterable(listOfLists)

N = int(raw_input())
vals = Counter(flatten([map(int, raw_input().split()) for _ in xrange(N)])).values()
print sum(e/2 for e in vals) + len(filter(lambda e: e&1, vals)) / 4