N = int(input())
power_up = 0
items = {}
for i in range(N):
    for j in input().split():
        items.setdefault(j,0)
        t = items[j] + 1
        if not t % 2:
            t = 0
            power_up+=1
        items[j] = t
power_up+=sum(items.values()) // 4
print(power_up)