#coding: UTF-8

import sys
from math import pi
from collections import deque
from functools import reduce

### defs ###

### main ###
N = int(sys.stdin.readline())
abc = map(lambda s:s.split(), sys.stdin.readlines())
abc = map(lambda lst: map(int,lst) ,abc)
cnt = [0]*10
for x in abc:
	for y in x:
		cnt[y-1]+=1

ans=0
for i in range(10):
	ans += cnt[i] // 2
	cnt[i] -= cnt[i]//2*2
ans += sum(cnt)//4
print(ans)