import sys
read = sys.stdin.buffer.read
readline = sys.stdin.buffer.readline
readlines = sys.stdin.buffer.readlines
sys.setrecursionlimit(10 ** 7)

from collections import Counter

n = int(readline())
check = []
for i in range(n):
    check += list(map(int, readline().split()))
counter = list(Counter(check).values())
cnt = 0
ans = 0
for v in counter:
    cnt += v % 2
    ans += v // 2
print(ans + cnt // 4)