import itertools
def dfs(item,d):
    if tuple(item) in memo: return memo[tuple(item)]
    res = 0
    for i in range(10):
        if item[i] >= 2:
            nitem = item[:]
            nitem[i] -= 2
            res = max(res,dfs(nitem[:],d+1))
    for select in itertools.combinations(range(10),4):
        if all(item[i] >= 1 for i in select):
            nitem = item[:]
            for i in select: nitem[i] -= 1
            res = max(res,dfs(nitem[:],d+1))
    res = max(res,d)
    memo[tuple(item)] = res
    return res
    
N = int(raw_input())
item = [0]*10
for loop in xrange(N):
    for i in map(int,raw_input().split()):
        item[i-1] += 1
memo = {}
print dfs(item[:],0)