N = int(input())
lsS = list(map(int,input().split()))
lsT = list(map(int,input().split()))
lsans = [[-1]*N for i in range(N)]
for i in range(N):
    if lsS[i] == 0:
        for j in range(N):
            lsans[i][j] = 0
for i in range(N):
    if lsT[i] == 0:
        for j in range(N):
            lsans[j][i] = 0
for i in range(N):
    if lsS[i] == 2:
        for j in range(N):
            lsans[i][j] = 1
for i in range(N):
    if lsT[i] == 2:
        for j in range(N):
            lsans[j][i] = 1
rmS = []
rmT = []
for i in range(N):
    if lsS[i] == 1:
        if lsans[i].count(1) != 0:
            continue
        rmS.append(i)
for i in range(N):
    if lsT[i] == 1:
        ii = 0
        for j in range(N):
            if lsans[j][i] == 1:
                ii += 1
                break
        if ii == 0:
            rmT.append(i)
maxl = max(len(rmS),len(rmT))
ans = maxl
for i in range(N):
    for j in range(N):
        if lsans[i][j] == 1:
            ans += 1
print(ans)