#coding:utf-8

N=input()
item_str=[raw_input().split() for i in range(N)]

item=[]
for i in item_str:
	item+=i

cnt=0
for i in xrange(1,11):

	if item.count(str(i))%2==0 and item.count(str(i))!=0:
		cnt+=item.count(str(i))/2
		for u in range(item.count(str(i))):
			item.remove(str(i))
			
	if item.count(str(i))%2==1 and item.count(str(i))!=1:
		cnt+=(item.count(str(i))-1)/2
		for u in range(item.count(str(i))-1):
			item.remove(str(i))
			
print cnt+len(item)/4