def count(d):
    result = 0
    for it in filter(lambda it: it[1] > 1, d.items()):
        q, r = divmod(it[1], 2)
        result += q
        d[it[0]] = r
    result += (sum(d.values()) // 4)
    return result

N = int(input())

D = {}
for _ in range(N):
    lst = input().split()
    for c in lst:
        if c in D:
            D[c] += 1
        else:
            D[c] = 1

print(count(D))