n=int(input())
m=[]
p=0
for i in range(n):
   m+=(map(int,input().split()))
while len(m)>len(set(m)):
  for i in set(m):
    print(m)
    if m.count(i)>1:
      m.remove(i)
      m.remove(i)
      p+=1
print(p+len(m)//4)