#include<bits/stdc++.h>
#include<algorithm>
#include<random>
#include<chrono>
#include<cstdlib>
#include<ctime>
#include<numeric>
#include<vector>
#include<stack>
#include<map>
#include<set>
#include<queue>
#include<iomanip>
#define int long long
#define ll long long
#define fi first
#define se second
#define pii pair<int,int>
#define sz(a) ((int)a.size())
#define FOR(i,j,k) for(int i=j;i<=k;i++)
#define REP(i,k,j) for(int i=k;i>=j;i--)
#define FORD(i,a) for(auto i:a)
#define rngdcl mt19937_64 rng(chrono::steady_clock::now().time_since_epoch().count())
#define random(l,r) ((l)+(rng()%(r-l+1)))
using namespace std;
const int nmax=5e5+1;
int n,crr=0;
int a[nmax],b[nmax];
map<int,int> mp;
set<int> s;
int L[nmax]; // log floor
// sparse table stored dynamically to avoid huge static allocation
vector<vector<int>> mn; // not really used but keep for parity
vector<vector<int>> mx;
int getmax(int x, int y)
{
if(x>y) swap(x,y);
int len = y - x + 1;
int LOG = L[len];
return max(mx[x][LOG], mx[y-(1<<LOG)+1][LOG]);
}
void build()
{
// compute logs
L[1] = 0;
for(int i=2;i<=n;i++) L[i]=L[i/2]+1;
int maxLog = L[n];
// allocate sparse table: indices 1..n, logs 0..maxLog
mx.assign(n+1, vector<int>(maxLog+1, 0));
mn.assign(n+1, vector<int>(maxLog+1, 0)); // kept if needed later
for(int i=1;i<=n;i++) // base case
{
mn[i][0]=a[i];
mx[i][0]=a[i];
}
for(int j=1;j<=maxLog;j++)
{
for (int i = 1; i + (1<<j) - 1 <= n; ++i)
{
mx[i][j]=max(mx[i][j-1],mx[i+(1<<(j-1))][j-1]);
mn[i][j]=min(mn[i][j-1],mn[i+(1<<(j-1))][j-1]);
}
}
}
struct BIT
{
vector<int> tree;
int n;
BIT (int N=0)
{
n=N;
tree.assign(n+5,0);
}
void update(int x,int val) {while(x<=n) { tree[x]=max(tree[x],val); x+=(x&-x);} }
int get(int x) { int ans=0; while(x>0) {ans=max(ans,tree[x]); x-=(x&-x);} return ans; }
};
void input()
{
cin >> n;
FOR(i,1,n) cin >> a[i];
FOR(i,1,n) cin >> b[i];
FOR(i,1,n) s.insert(a[i]);
// map values in increasing order (1-based ranks)
FORD(val, s) mp[val]=++crr;
FOR(i,1,n)
{
a[i]=mp[a[i]];
if(mp.count(b[i])) b[i]=mp[b[i]];
else b[i]=0;
}
}
signed main()
{
ios_base::sync_with_stdio(false); cin.tie(NULL); cout.tie(NULL);
input();
// allocate pos according to compressed size
vector<vector<int>> pos(crr+1);
FOR(i,1,n) pos[a[i]].push_back(i);
build();
BIT bit(n); // sized by n
vector<pair<int,int>> ops;
// collect ops in same order as original logic: for each i in B, push valid positions of that value (right->left)
FOR(i,1,n)
{
if(!b[i]) continue;
for(int j = (int)pos[b[i]].size()-1; j>=0; --j)
{
int id = pos[b[i]][j];
if(getmax(id,i) > b[i]) continue;
int pre = bit.get(id);
bit.update(id, pre+1);
}
}
cout << bit.get(n) << '\n';
return 0;
}
