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
cnt = 0
for i in range(10):
    ans += item_cnt[i]//2
    if item_cnt[i]%2:
        cnt += 1

print(ans+cnt//4)