N = int(input())
item_cnt = [0]*10
for _ in range(N):
    item = list(map(int,input().split()))
    for i in item:
        item_cnt[i-1] += 1

ans = 0
for i in range(10):
    power = item_cnt[i]//2
    ans += power
    item_cnt[i] -= power*2

if item_cnt.count(1) >= 8:
    ans += 2
elif item_cnt.count(1) >= 4:
    ans += 1

print(ans)