import sys
input = sys.stdin.readline

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

ANS=[[-1]*N for i in range(N)]

for i in range(N):
    if S[i]==0:
        for j in range(N):
            ANS[i][j]=0
    elif S[i]==2:
        for j in range(N):
            ANS[i][j]=1

    if T[i]==0:
        for j in range(N):
            ANS[j][i]=0
    elif T[i]==2:
        for j in range(N):
            ANS[j][i]=1

score=0
R=[0]*N
C=[0]*N

for i in range(N):
    for j in range(N):
        if ANS[i][j]==1:
            score+=1
            R[i]=-1
            C[j]=-1

        elif ANS[i][j]==-1:
            if R[i]!=-1:
                R[i]=1
            if C[j]!=-1:
                C[j]=1

print(score+max(R.count(1),C.count(1)))