#include <bits/stdc++.h>
using namespace std;
typedef int ll;
ll INF = 1e9+7;
ll MOD = 998244353;
typedef pair<ll,ll> ii;
#define iii pair<ii,ll>
#define f(i,a,b) for(ll i = a;i < b;i++)
#define pb push_back
#define vll vector<ll>
#define F first
#define S second
#define all(x) (x).begin(), (x).end()
///I hope I will get uprating and don't make mistakes
///I will never stop programming
///sqrt(-1) Love C++
///Please don't hack me
///@TheofanisOrfanou Theo830
///Think different approaches (bs,dp,greedy,graphs,shortest paths,mst)
///Stay Calm
///Look for special cases
///Beware of overflow and array bounds
///Think the problem backwards
///Training
ll seg[400005]={0};
void update(ll s,ll e,ll qs,ll qe,ll idx,ll k){
if(s == e && s == qs){
seg[idx] = max(seg[idx],k);
return;
}
if(qs > e || qe < s){
return;
}
ll mid = (s+e)/2;
update(s,mid,qs,qe,idx*2,k);
update(mid+1,e,qs,qe,idx*2+1,k);
seg[idx] = max(seg[idx*2],seg[idx*2+1]);
}
ll query(ll s,ll e,ll qs,ll qe,ll idx){
if(qs <= s && e <= qe){
return seg[idx];
}
if(qs > e || qe < s){
return 0;
}
ll mid = (s+e)/2;
ll a = query(s,mid,qs,qe,idx*2);
ll b = query(mid+1,e,qs,qe,idx*2+1);
return max(a,b);
}
int main(void){
ios_base::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
ll n;
cin>>n;
ll a[n],b[n];
map<ll,ll>mp;
bool ok1 = 1,ok2 = 1;
f(i,0,n){
cin>>a[i];
if(mp[a[i]] == 1){
ok1 = 0;
}
mp[a[i]]++;
}
f(i,0,n){
cin>>b[i];
if(b[i] != b[0]){
ok2 = 0;
}
}
if(ok2){
ll ans = 0;
ll ok = 0;
ll posa = 0;
f(i,0,n){
if(a[i] > b[0]){
ans += posa * ok;
ok = 0;
posa = 0;
}
else{
posa++;
ok |= (a[i] == b[0]);
}
}
ans += posa * ok;
cout<<ans<<endl;
return 0;
}
if(ok1 && n > 5000){
ll l[n],r[n];
priority_queue<ii,vector<ii>,greater<ii> >pq;
f(i,0,n){
pq.push(ii(a[i],i));
while(pq.top().F < a[i]){
r[pq.top().S] = i-1;
pq.pop();
}
}
while(!pq.empty()){
r[pq.top().S] = n-1;
pq.pop();
}
for(ll i=n-1;i >= 0;i--){
pq.push(ii(a[i],i));
while(pq.top().F < a[i]){
l[pq.top().S] = i+1;
pq.pop();
}
}
while(!pq.empty()){
l[pq.top().S] = 0;
pq.pop();
}
ll ans = 0;
ll dp[n+1];
dp[0] = 0;
f(i,1,n+1){
dp[i] = 0;
if(b[i-1] == INF || !(l[b[i-1]-1] <= i-1 && i-1 <= r[b[i-1]-1])){
continue;
}
dp[i] = query(1,n+1,1,b[i-1],1) + 1;
update(1,n+1,b[i-1],b[i-1],1,dp[i]);
ans = max(ans,dp[i]);
}
cout<<ans<<endl;
return 0;
}
ll l[n],r[n];
priority_queue<ii,vector<ii>,greater<ii> >pq;
f(i,0,n){
pq.push(ii(a[i],i));
while(pq.top().F < a[i]){
r[pq.top().S] = i-1;
pq.pop();
}
}
while(!pq.empty()){
r[pq.top().S] = n-1;
pq.pop();
}
for(ll i=n-1;i >= 0;i--){
pq.push(ii(a[i],i));
while(pq.top().F < a[i]){
l[pq.top().S] = i+1;
pq.pop();
}
}
while(!pq.empty()){
l[pq.top().S] = 0;
pq.pop();
}
ll dp[n+1][n+1];
f(i,0,n+1){
f(j,0,n+1){
if(i == 0 || j == 0){
dp[i][j] = 0;
}
else{
dp[i][j] = max(dp[i-1][j],dp[i][j-1]);
if(a[i-1] == b[j-1] && (l[i-1] <= j-1 && j-1 <= r[i-1])){
dp[i][j] = max(dp[i][j],dp[i][j-1] + 1);
}
}
}
}
cout<<dp[n][n]<<endl;
}
