from collections import defaultdict


def main():
    items = defaultdict(int)
    powerup_count = 0
    for _ in range(int(input())):
        for number in map(int, input().split()):
            if items[number] == 1:
                powerup_count += 1
                items[number] = 0
            else:
                items[number] += 1

    powerup_count += sum(items.values()) // 4
    print(powerup_count)


if __name__ == "__main__":
    main()