N = int(input())
l = []
for i in range(N):
    l += input().split()
d = {}
for i in set(l):
    d[i] = l.count(i)
ans = 0
m = 0
for k, v in d.items():
    if v >= 2:
        ans += v//2
    m += v%2
print(ans + m // 4)