item = []
memo = []
delete = []
r = 0
N = int(input())

for i in range(N):
    item+=input().split(' ')

for s in range(len(item)):
    if item[s] in memo:
        continue
    c = item.count(item[s]) // 2
    if c >= 1:
        delete.append(item[s])
    memo.append(item[s])
    r+=c
for d in delete:
    memo.remove(d)
r+= len(memo) // 4
print(int(r))