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

yoko = 0
tate = 0
ans = 0
dat = [[-1] * N for _ in range(N)]
sflag = False
tflag = False
for i in range(N):
    for j in range(N):
        if S[i] == 0 or T[j] == 0:
            dat[i][j] = 0
        elif S[i] == 2 or T[j] == 2:
            ans += 1
            dat[i][j] = 1
for s in S:
    if s == 1:
        yoko += 1
    elif s == 2:
        sflag = True
for t in T:
    if t == 1:
        tate += 1
    elif t == 2:
        tflag = True
        
if sflag and tflag:
    pass
elif not sflag and tflag:
    ans += tate
elif not tflag and sflag:
    ans += yoko
else:
    ans += max(yoko,tate)
print(ans)