from collections import Counter
n = int(input())
array = [list(map(int,input().split())) for i in range(n)]
array = Counter(sum(array,[]))
array = sorted(array.values())[::-1]
count = 0
for i,v in enumerate(array):
    while v>=2:
        v-=2
        array[i]-=2
        count+=1
print(sum(array)//4+count)