#include <bits/stdc++.h>
using namespace std;
const int N = 1e5+10, K = 20;
#define pb push_back
int n, a[N], b[N], rmq[N][K];
map<int, vector<int>> m;
int subtask2(){
int ans = 0;
vector<bool> is_taken(n + 5, 0);
for(int i = 1; i <= n; i++){
if(a[i] == b[1]){
ans++;
int l = i-1, r = i + 1;
is_taken[i] = 1;
for(; l >= 1 && !is_taken[l] && a[l] < b[1]; l--) ans++, is_taken[l] = 1;
for(; r <= n && !is_taken[r] && a[r] < b[1]; r++) ans++, is_taken[r] = 1;
}
}
return ans;
}
int Q(int l, int r){
int k = __lg((r-l+1));
return max(rmq[l][k], rmq[r - (1<<k) + 1][k]);
}
int subtask4(){
map<int, int> m;
for(int i = 1; i <= n; i++) m[a[i]] = i;
vector<int> dp(n+2);
for(int i = 1; i <= n; i++){
dp[i] = dp[i - 1];
if(a[i] <= b[i]){
int pos = m[b[i]];
if(pos > 0 && Q(min(i, pos), max(i, pos)) <= b[i]){
dp[i]++;
}
}
}
return dp[n];
}
void precalc(){
for(int i = 1; i <= n; i++) rmq[i][0] = a[i];
for(int j = 1; j < K; j++){
for(int i = 1; i + (1<<j) <= n + 1; i++){
rmq[i][j] = max(rmq[i][j - 1], rmq[i + (1<<(j-1))][j - 1]);
}
}
}
int main(){
cin.tie(0); ios::sync_with_stdio(0);
cin >> n;
for(int i = 1; i <= n; i++) cin >> a[i];
for(int i = 1; i <= n; i++) cin >> b[i];
precalc();
bool is_b = 1;
for(int i = 2; i <= n; i++) if(b[i] != b[i - 1]) is_b = 0;
if(is_b){
cout << subtask2();
return 0;
}
if(n > 5000){
cout << subtask4();
return 0;
}
int ans = 0;
vector<vector<int>> dp(n+2, vector<int>(n+2));
for(int i = 1; i <= n; i++){
int mx = 0;
for(int j = 1; j <= n; j++){
int x = Q(min(i, j), max(i, j));
mx = max(mx, dp[i - 1][j]);
if(x > b[i]){
dp[i][j] = mx;
}else{
if(a[i] <= b[i] && a[j] == b[i]){
dp[i][j] = mx + 1;
}else dp[i][j] = mx;
}
if(i==n) ans=max(ans, dp[i][j]);
}
}
cout << ans;
return 0;
}
