import collections
a=int(input())
b=[input().split() for i in range(a)]

c=[]
for i in b:
    for j in i:
        c.append(j)
d=collections.Counter(c)
e=0
f=0

for i in d:
    e+=d[i]//2
    if d[i]%2==1:
        f+=1
        
e+=f//4
print(e)