n = int(input())
s = list(map(int, input().split()))  # 行情報
t = list(map(int, input().split()))  # 列情報

row = [0] * n
col = [0] * n

u = [[False] * n for _ in range(n)]

ans = 0
for i in range(n):
    if s[i] == 2:
        for j in range(n):
            if not u[i][j]:
                ans += 1
                col[j] += 1
                u[i][j] = True
    if t[i] == 2:
        for j in range(n):
            if not u[j][i]:
                ans += 1
                row[j] += 1
                u[j][i] = True

for i in range(n):
    for j in range(n):
        if s[i] == 1 and t[j] == 1:
            if row[i] == 0 and col[j] == 0:
                ans += 1
                row[i] += 1
                col[j] += 1

for i in range(n):
    if s[i] == 1 and row[i] == 0:
        ans += 1
    if t[i] == 1 and col[i] == 0:
        ans += 1

print(ans)