// #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], mx[N];
int f[N];
vector<int> g[2 * N];
void upd(int i, int x){
while(i <= n){
f[i] = max(f[i], x);
i += i & -i;
}
}
int get(int i){
int res = 0;
while(i){
res = max(res, f[i]);
i -= i & -i;
}
return res;
}
void dnc(int l, int r, int optl, int optr, int x){
if(l > r) return;
int mid = (l + r) / 2;
int cur = 0, optp = 0;
for(int i = optl; i <= min(mid, optr); i++){
int res = get(g[x][i] - 1) + (mid - i + 1);
if(res > cur){
cur = res;
optp = i;
}
}
dnc(l, mid - 1, optl, optp, x);
dnc(mid + 1, r, optp, optr, x);
upd(g[x][mid], cur);
}
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]);
}
for(int i = 1; i <= 2 * n; i++){
g[i].push_back(0);
}
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;
g[b[i]].push_back(i);
}
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 l[2 * n + 1] = {}, r[2 * n + 1] = {};
for(int i = 1; i <= n; i++){
int x = a[i];
while(r[x] < g[x].size() && g[x][r[x]] < R[i] && g[x][r[x]] <= i) r[x]++;
if(g[x][r[x]] >= R[i]) r[x]--;
while(l[x] < g[x].size() && g[x][l[x]] <= L[i]) l[x]++;
if(l[x] > r[x] || l[x] >= g[x].size() || r[x] >= g[x].size()) continue;
dnc(l[x], r[x], l[x], r[x], x);
}
cout << get(n);
}
signed main(){
SS
// freopen("trains.in", "r", stdin);
// freopen("trains.out", "w", stdout);
int t = 1;
// cin >> t;
while(t--){
solve();
}
}
