n = int(input())
i = [0]*10

for _ in range(n):
    p = list(map(int,input().split()))
    for j in p:
        i[j-1] += 1
a,b = 0,0
for j in i:
    a += j // 2
    if j == 1:
        b += 1
        if b % 4 == 0:
            a += 1
print(a)