mod = 1000000007
eps = 10**-9


def main():
    import sys
    input = sys.stdin.readline

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

    A = [[0] * N for _ in range(N)]
    for i in range(N):
        if S[i] == 2:
            for j in range(N):
                A[i][j] = 1
    for i in range(N):
        if T[i] == 2:
            for j in range(N):
                A[j][i] = 1

    ans = 0
    for i in range(N):
        for j in range(N):
            ans += A[i][j]

    if ans != 0:
        for i in range(N):
            if S[i] == 1 and max(A[i]) == 0:
                ans += 1
        for j in range(N):
            if T[j] == 1:
                flg = 1
                for i in range(N):
                    if A[i][j] == 1:
                        flg = 0
                        break
                if flg:
                    ans += 1
    else:
        s = sum(S)
        t = sum(T)
        ans = max(s, t)
    print(ans)


if __name__ == '__main__':
    main()