cnt=[];chk1=chk2=0
x=sum([[*map(int,input().split())] for _ in range(int(input()))],[])
for i in set(x):
    cnt.append(x.count(i))
for i in cnt:
    while i>=2:
        chk1+=1
        i-=2
    if i==1:
        chk2+=1
print(chk1+chk2//4)