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 j in range(n):
    if T[j] == 2:
        for i in range(n):
            A[i][j] = 1
            
c1 = 0
for i in range(n):
    if S[i] == 1:
        ok = False
        for j in range(n):
            if A[i][j] == 1:
                ok = True
                break
        if not ok:
            c1 += 1
            
c2 = 0
for j in range(n):
    if T[j] == 1:
        ok = False
        for i in range(n):
            if A[i][j] == 1:
                ok = True
                break
        if not ok:
            c2 += 1
            
ans = sum(sum(row) for row in A) + max(c1, c2)
print(ans)