N = int(input())

dic = {}
for i in range(N):
  a = input().split(' ')
  for j in range(len(a)):
    try:
      dic[a[j]] += 1
    except:
      dic[a[j]] = 1

cnt1 = 0
cnt2 = 0
for i in dic.keys():
  cnt1 += dic[i] // 2
  cnt2 += dic[i] % 2

print(cnt1 + (cnt2 // 4))