N = int(input())
S = list(map(int, input().split()))
T = list(map(int, input().split()))

check = [[-1] * (N) for _ in range(N)]

for i, s in enumerate(S):
    if S[i] == 0: # 全部0
        for j in range(N):
            check[i][j] = 0
    elif S[i] == 2:
        for j in range(N):
            check[i][j] = 1

for j, t in enumerate(T):
    if T[j] == 0:
        for i in range(N):
            check[i][j] = 0
    elif T[j] == 2:
        for i in range(N):
            check[i][j] = 1

ans = 0
for i in range(N):
    for j in range(N):
        if check[i][j] == 1:
            ans += 1
            if S[i] == 1:
                S[i] = 3
            if T[j] == 1:
                T[j] = 3

ans += max(S.count(1), T.count(1))
print(ans)