n = int(input())
l = [list(map(int, input().split())) for _ in range(n)]

d = {}
for i in l:
    for j in i:
        if not j in d:
            d[j] = 1
        else:
            d[j] += 1

l = list(d.values())
c = 0
for i in l:
    if i > 1:
        c += i//2

c1 = l.count(1)
c += c1 // 4

print(c)