l ={i+1:0 for i in range(10)}
N = int(input())
for _ in range(N):
    m =[int(i) for i in input().split()]
    for i in m:
        l[i] += 1

ans = 0
for i in l.values():
    ans += i // 2
ans += (sum(l.values())-2*ans)//4
print(ans)