// #pragma optimize ("g",on)
// #pragma GCC optimize ("inline")
// #pragma GCC optimize ("Ofast")
// #pragma GCC optimize ("unroll-loops")
// #pragma GCC optimize ("03")
#include <bits/stdc++.h>
#define pb push_back
#define SS ios_base::sync_with_stdio(0);cin.tie(nullptr);cout.tie(nullptr);
#define int long long
#define all(v) v.begin(),v.end()
using namespace std;
mt19937 rnd(chrono::steady_clock::now().time_since_epoch().count());
const int N = 5001, inf = 1e9, mod = 998244353;
int n;
int a[N], b[N];
int t[4 * N], add[4 * N];
void upd(int v, int tl, int tr, int pos, int x){
if(tl == tr){
t[v] = max(t[v], x);
return;
}
int mid = (tl + tr) / 2;
if(mid >= pos) upd(v * 2, tl, mid, pos, x);
else upd(v * 2 + 1, mid + 1, tr, pos, x);
t[v] = max(t[v * 2], t[v * 2 + 1]);
}
int get(int v, int tl, int tr, int l, int r){
if(tl > r || l > tr || l > r) return 0;
if(tl >= l && r >= tr) return t[v];
int mid = (tl + tr) / 2;
return max(get(v * 2, tl, mid, l, r), get(v * 2 + 1, mid + 1, tr, l, r));
}
void solve(){
cin >> n;
vector<int> v;
for(int i = 1; i <= n; i++){
cin >> a[i];
v.push_back(a[i]);
}
for(int i = 1; i <= n; i++){
cin >> b[i];
v.push_back(b[i]);
}
sort(all(v));
v.erase(unique(all(v)), v.end());
for(int i = 1; i <= n; i++){
a[i] = lower_bound(all(v), a[i]) - v.begin() + 1;
b[i] = lower_bound(all(v), b[i]) - v.begin() + 1;
}
stack<int> st;
int R[n + 1] = {}, L[n + 1] = {};
for(int i = n; i >= 1; i--){
while(st.size() && a[st.top()] <= a[i]) st.pop();
if(st.size()) R[i] = st.top();
else R[i] = n + 1;
st.push(i);
}
while(st.size()) st.pop();
for(int i = 1; i <= n; i++){
while(st.size() && a[st.top()] <= a[i]) st.pop();
if(st.size()) L[i] = st.top();
st.push(i);
}
int ans[n + 1][n + 1] = {};
for(int i = 1; i <= n; i++){
int cnt[n + 1] = {}, mx = 0;
for(int j = i; j <= n; j++){
cnt[b[j]]++;
mx = max(mx, a[j]);
ans[i][j] = cnt[mx];
}
}
for(int i = 1; i <= n; i++){
for(int l = i; l > L[i]; l--){
for(int r = i; r < R[i]; r++){
upd(1, 1, n, r, ans[l][r] + get(1, 1, n, 1, l - 1));
}
}
}
cout << t[1];
}
signed main(){
SS
// freopen("trains.in", "r", stdin);
// freopen("trains.out", "w", stdout);
int t = 1;
// cin >> t;
while(t--){
solve();
}
}
