n=int(input())
s=list(map(int,input().split()))
t=list(map(int,input().split()))
a=[[None]*n for _ in range(n)]
row1,col1=False,False
cnt_row,cnt_col=0,0
ans=0
for i,x in enumerate(s):
  if x==0:
    for j in range(n):
      a[i][j]=0
  elif x==2:
    for j in range(n):
      a[i][j]=1
    row1=True
  else:
    cnt_row+=1
for i,x in enumerate(t):
  if x==0:
    for j in range(n):
      a[j][i]=0
  elif x==2:
    for j in range(n):
      a[j][i]=1
    col1=True
  else:
    cnt_col+=1
for y in a:
  for x in y:
    if x is not None:ans+=x
if col1 and row1:
  pass
elif col1:
  ans+=cnt_col
elif row1:
  ans+=cnt_row
else:
  ans+=max(cnt_row,cnt_col)
print(ans)
#for x in a:print(x)