N=int(input())
S=list(map(int,input().split()))
T=list(map(int,input().split()))
A=[[0]*N for i in range(N)]
for i in range(N):
  if S[i]==0:
    for j in range(N):
      A[i][j]=0
  if 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
  if T[i]==2:
    for j in range(N):
      A[j][i]=1
X,Y=0,0
for i in range(N):
  if S[i]==1:
    for j in range(N):
      if A[i][j]==1:
        break
      if j==N-1:
        X+=1
  if T[i]==1:
    for j in range(N):
      if A[j][i]==1:
        break
      if j==N-1:
        Y+=1
print(sum([sum(A[i]) for i in range(N)])+max(X,Y))