n = int(input())

l = [0] * 11
for i in range(n):
    m = list(map(int, input().split()))
    for j in m:
        l[j] += 1

l2 = []
x = 0
for i in l:
    if i >= 2:
        x += i//2
        l2.append(i - (i//2) * 2)
    else:
        l2.append(i)

print(x + l2.count(1)//4)