# -*- coding:utf-8 -*-
if __name__ == '__main__':
    n = int(input())
    an = []
    for i in range(n):
        an.extend(map(int, input().split()))
    d = {k: 0 for k in set(an)}
    for a in an:
        d[a] += 1
    cnt = 0
    for k, v in d.items():
        cnt, d[k] = cnt + int(v / 2), v % 2
    print(cnt + int(sum(d.values()) / 4))