#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef long double ld;
#define vc vector
typedef vc<ll> vcll;
typedef vc<bool> vcb;
#define pr pair
typedef pr<ll, ll> prll;
typedef set<ll> setll;
typedef map<ll,ll> mapll;
#define uset unordered_set
typedef uset<ll> usetll;
#define umap unordered_map
typedef umap<ll,ll> umapll;
#define f0r(i,a,n) for ((i)=(a); (i)<=(n); (i)++)
#define r0f(i,n,a) for ((i)=(n); (i)>=(a); (i)--)
#define pb push_back
#define ppb pop_back
#define pf push_front
#define ppf pop_front
#define mp make_pair
#define fi first
#define se second
#define sz size
#define all(x) (x).begin(), (x).end()
#define all0(x, n) (x).begin(), (x).begin()+n
#define all1(x, n) (x).begin()+1, (x).begin()+n+1
#define allrev(x) (x).rbegin(), (x).rend()
#define in(v, s) ((s).find((v)) != (s).end())
#define GCD(x, y) __gcd(abs((x)), abs((y)))
#define INF (LLONG_MAX>>3ll)
#define MOD (1'000'000'007ll)
#define mxN (100'010ll)
#define lgN (17ll)
#define sgN (1ll<<17ll)
inline void maxa(ll &a, ll b) { if (a<b) a=b; }
inline void mina(ll &a, ll b) { if (a>b) a=b; }
inline void print (vcll &a, ll n=-1, string name="")
{
cout << name << ": ";
if (n==-1) for (ll x:a) printf("%lli ", x);
else
{
ll i;
f0r(i,1,n) printf("%lli ", a[i]);
}
printf("\n");
}
ll n;
vcll a(mxN), b(mxN);
vc<vcll> arrows0(mxN);
vc<vcll> arrows1(mxN);
struct ST // range max queries
{
vcll st;
inline ST() { st.resize(sgN*2+10, 0); }
ll qry (ll it, ll lt, ll rt, ll l, ll r)
{
if (rt<=l or r<=lt) return 0;
if (l<=lt and rt<=r) return st[it];
ll i2=it*2, mt=(lt+rt)/2;
return max(qry(i2,lt,mt,l,r), qry(i2+1,mt,rt,l,r));
}
inline ll qry (ll l, ll r) { return qry(1,0,n+1,l,r+1); }
inline ll upd (ll it, ll lt, ll rt, ll j, ll x)
{
if (j<lt or rt<=j) return st[it];
if (lt+1==rt) return st[it] = max(st[it],x);
ll i2=it*2, mt=(lt+rt)/2;
return st[it] = max(upd(i2,lt,mt,j,x), upd(i2+1,mt,rt,j,x));
}
inline void upd (ll j, ll x) { upd(1,0,n+1,j,x); }
} stg, dp0, dp1;
mapll lasti;
inline void bd_arrows()
{
ll i;
f0r(i,1,n) stg.upd(i,a[i]);
f0r(i,1,n)
{
if (in(b[i], lasti) and a[i]!=b[i])
{
ll j=lasti[b[i]];
if (stg.qry(j,i) == a[j]) arrows0[i].pb(j);
}
lasti[a[i]]=i;
}
lasti.clear();
r0f(i,n,1)
{
if (in(b[i], lasti) and a[i]!=b[i])
{
ll j=lasti[b[i]];
if (stg.qry(i,j) == a[j]) arrows1[j].pb(i);
}
lasti[a[i]]=i;
}
f0r(i,1,n) if (a[i]==b[i]) arrows1[i].pb(i);
f0r(i,1,n) sort(all(arrows0[i]));
f0r(i,1,n) sort(all(arrows1[i]));
}
inline void doq1 (ll i, ll j)
{
ll x = dp1.qry(1,j-1) + 1;
dp1.upd(j,x);
dp0.upd(i,x);
}
inline void doq0 (ll i, ll j)
{
ll x = dp0.qry(1,j) + 1;
dp0.upd(j,x);
dp1.upd(i,x);
}
inline void bd_dp()
{
ll i;
f0r(i,1,n)
{
for (ll j:arrows1[i]) doq1(i,j);
for (ll j:arrows0[i]) doq0(i,j);
}
}
inline void main2()
{
scanf("%lli", &n);
ll i;
f0r(i,1,n) scanf("%lli", &a[i]);
f0r(i,1,n) scanf("%lli", &b[i]);
bd_arrows();
bd_dp();
printf("%lli\n", max(dp0.qry(1,n), dp1.qry(1,n)));
}
int main()
{
// cin.tie(0); cout.tie(0);
// ios_base::sync_with_stdio(0);
srand(time(0));
// freopen("file.in", "r", stdin);
ll t=1;
// scanf("%lli", &t);
while (t--) main2();
return 0;
}
