l=[0]*100
N=int(input())
for e in range(N):
    a=map(int, input().split())
    for b in a:
        l[b-1]+=0.5
l=[x for x in l if x != 0]
L=[[x//1, x-x//1] for x in l]
u=0
v=0
for x,y in L:
    u+=x
    v+=y
print(int(u+v//2))