N=int(input())
i_l=[]

for i in range(N):
    a=list(map(int,input().split()))
    i_l.extend(a)

import collections

c = collections.Counter(i_l)
cnt=0
for k,v in c.items():
    if v//2>0:
        cnt+=v//2
        c[k]=c[k]-2*(v//2)

keys=[k for k, v in c.items() if v==1]
num=len(keys)

if num//4>0:
    cnt+=num//4

print(cnt)