#include <bits/stdc++.h>
using namespace std;
int n, k, ans = -1;
int a1[1000001], b1[1000001], a[1000001], b[1000001], t[1000001], d[1000001],
    in[1000001], Max[2000001];
int s = 1;
int getmax(int v, int vl, int vr, int l, int r) {
  if (l > vr || r < vl) {
    return 0;
  }
  if (vl >= l && vr <= r) {
    return Max[v];
  }
  return max(getmax(v * 2, vl, (vl + vr) / 2, l, r),
             getmax(v * 2 + 1, (vl + vr) / 2 + 1, vr, l, r));
}
void update(int v) {
  v /= 2;
  if (v <= 0) {
    return;
  }
  Max[v] = max(Max[v * 2], Max[v * 2 + 1]);
  update(v);
}
int main() {
  cin >> n;
  for (int i = 0; i < n; i++) {
    cin >> a1[i];
    t[a1[i]] = i + 1;
  }
  for (int i = 0; i < n; i++) {
    cin >> b1[i];
  }
  for (int i = 0; i < n; i++) {
    a[i] = i;
    b[i] = t[b1[i]];
  }
  while (n > s) {
    s *= 2;
    k++;
  }
  for (int i = 1; i < 2 * s; i++) {
    Max[i] = 0;
  }
  for (int i = 0; i < n; i++) {
    d[i] = getmax(1, 1, s, b[i], n) + 1;
    Max[s + b[i] - 1] = d[i];
    update(s + b[i] - 1);
  }
  for (int i = 0; i < n; i++) {
    ans = max(ans, d[i]);
  }
  cout << ans << endl;
  return 0;
}
