n = int(input())
s = list(map(int, input().split()))  # 行情報
t = list(map(int, input().split()))  # 列情報
# 0: or 0, 1: or 1, 2: and 1
u = [[False] * n for _ in range(n)]

ans = 0
for i in range(n):
    if s[i] == 2:
        for j in range(n):
            u[i][j] = True
            ans += 1
    if t[i] == 2:
        for j in range(n):
            u[j][i] = True
            ans += 1

for i in range(n):
    for j in range(n):
        if u[i][j]:
            continue
        if s[i] == 1 and t[j] == 1:
            ok1 = False
            ok2 = False
            for k in range(n):
                ok1 |= u[i][k]
                ok2 |= u[k][j]
            if not ok1 and not ok2:
                ans += 1
                u[i][j] = True

for i in range(n):
    for j in range(n):
        if u[i][j]:
            continue
        if s[i] == 1 and t[j] == 1:
            ok1 = False
            ok2 = False
            for k in range(n):
                ok1 |= u[i][k]
                ok2 |= u[k][j]
            if not (ok1 and ok2):
                ans += 1
                u[i][j] = True
print(ans)