N = int(input())
S = list(map(int,input().split()))
T = list(map(int,input().split()))
A = [[-1 for _ in range(N)] for _ in range(N)]
for i in range(N):
    if S[i]==0:
        for j in range(N):
            A[i][j] = 0
    elif S[i]==2:
        for j in range(N):
            A[i][j] = 1
    if T[i]==0:
        for j in range(N):
            A[j][i] = 0
    elif T[i]==2:
        for j in range(N):
            A[j][i] = 1
ans = 0
for i in range(N):
    for j in range(N):
        if A[i][j]==1:
            ans += 1
row = []
for i in range(N):
    if S[i]==1:
        if max(A[i])<=0:
            row.append(i)
col = []
for j in range(N):
    if T[j]==1:
        if max([A[i][j] for i in range(N)])<=0:
            col.append(j)
ans += max(len(row),len(col))
print(ans)