n = int(input())
a = list(map(int,input().split()))
count = 0

while a:
    word = a[0]
    if a.count(word) >= 2:
        count += a.count(word) // 2

    new_words = []
    for i in a:
        if i != word:
            new_words.append(i)
    
    a = new_words
print(count)