# coding: utf-8

n = int(input())
table = {}
count = 0
for i in range(n):
    l = list(map(int,input().split(" ")))
    for j in l:
        if j not in table:
            table[j] = 1
        else:
            table[j] += 1
        if table[j] == 2:
            count += 1
            table[j] = 0
print(count + sum(table.values()) // 4)