from collections import Counter
lst=[]
cnt1=0
cnt2=0
n = int(input())
for i in range(n):
    lst += list(map(int, input().split()))
count = sorted(Counter(lst).values(), reverse=1)
for c in count:
    if c>1:
        cnt1 += c//2
        cnt2 += c%2
    if c==1:
        cnt2 += 1
point = cnt1 * 1 + cnt2 // 4
print(point)