def main():

  power_up  = 0
  item_list = []
  item_dict = {}
  vs = int(input())
  for _ in range(vs):
    item_list.append(list(map(int, input().split())))
  for i in item_list:
    for s in i:
      if s in item_dict:
        item_dict[s] += 1
      else:
        item_dict[s] = 1
  item_value = list(item_dict.values())
  for i, value in enumerate(item_value):
    if value >= 2:
      same_count = value // 2
      power_up += same_count
      item_value[i] = value % 2
    else:
      continue
  amari = sum(item_value)
  amari_count = amari // 4
  power_up += amari_count
  print(power_up)

if __name__ == '__main__':
  main()