from collections import Counter

n = int(input())
count = Counter()

for i in range(n):
    for j in input().split():
        count[j] += 1

result = sum(map(lambda c: c[1] // 2, count.most_common()))
result += sum(map(lambda c: c[1] % 2, count.most_common())) // 4
print(result)