N = int(raw_input())
item = [0]*10
for loop in xrange(N):
    for i in map(int,raw_input().split()):
        item[i-1] += 1
ans = 0
for i in range(10):
    ans += item[i]/2
    item[i] %= 2
while item.count(0) <= 6:
    for i in range(10):
        item[i] = max(0,item[i]-1)
    ans += 1
print ans