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

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

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

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

s = 0
t = 0

for i in range(N):
    if S[i] == 1:
        for j in range(N):
            if A[i][j] == 1:
                break
        else:
            s += 1

for j in range(N):
    if T[j] == 1:
        for i in range(N):
            if A[i][j] == 1:
                break
        else:
            t += 1

print(max(s, t) + sum(map(sum, A)))