#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  cin >> n;
  vector<int> a(n + 1), b(n + 1), pos(n + 1, 0);
  for (int i = 1; i <= n; i++) {
    cin >> a[i];
  }
  for (int i = 1; i <= n; i++) {
    cin >> b[i];
    pos[b[i]] = i;
  }
  int ans = 0;
  for (int i = 1; i < n; i++) {
    if (pos[a[i]] > pos[a[i + 1]]) {
      ans = n - i;
      break;
    }
  }
  cout << ans << '\n';
}
