#include <bits/stdc++.h>
using namespace std;
template <class T>
inline int lb(vector<T> &v, const T &x) {
  return lower_bound(v.begin(), v.end(), x) - v.begin();
}
template <class T>
inline int ub(vector<T> &v, const T &x) {
  return upper_bound(v.begin(), v.end(), x) - v.begin();
}
template <class T>
inline int lb(T *v, int n, const T &x) {
  return lower_bound(v, v + n, x) - v;
}
template <class T>
inline int ub(T *v, int n, const T &x) {
  return upper_bound(v, v + n, x) - v;
}
template <class A, class B>
ostream &operator<<(ostream &f, const pair<A, B> &x) {
  return f << '(' << x.first << ", " << x.second << ')';
}
template <class T>
ostream &operator<<(ostream &f, const vector<T> &x) {
  int b = 0;
  f << '[';
  for (auto &y : x) {
    if (b++) f << ", ";
    f << y;
  }
  return f << ']';
}
template <class T, class C>
ostream &operator<<(ostream &f, const set<T, C> &x) {
  int b = 0;
  f << '[';
  for (auto &y : x) {
    if (b++) f << ", ";
    f << y;
  }
  return f << ']';
}
template <class T, class C>
ostream &operator<<(ostream &f, const multiset<T, C> &x) {
  int b = 0;
  f << '[';
  for (auto &y : x) {
    if (b++) f << ", ";
    f << y;
  }
  return f << ']';
}
template <class K, class T, class C>
ostream &operator<<(ostream &f, const map<K, T, C> &x) {
  int b = 0;
  f << '[';
  for (auto &y : x) {
    if (b++) f << ", ";
    f << y;
  }
  return f << ']';
}
template <class K, class T, class C>
ostream &operator<<(ostream &f, const multimap<K, T, C> &x) {
  int b = 0;
  f << '[';
  for (auto &y : x) {
    if (b++) f << ", ";
    f << y;
  }
  return f << ']';
}
template <class T>
ostream &operator<<(ostream &f, queue<T> x) {
  int b = 0;
  f << '[';
  while (x.size()) {
    if (b++) f << ", ";
    f << x.front();
    x.pop();
  }
  return f << ']';
}
template <class T>
ostream &operator<<(ostream &f, stack<T> x) {
  int b = 0;
  f << '[';
  while (x.size()) {
    if (b++) f << ", ";
    f << x.top();
    x.pop();
  }
  return f << ']';
}
template <class T, class V, class C>
ostream &operator<<(ostream &f, priority_queue<T, V, C> x) {
  int b = 0;
  f << '[';
  while (x.size()) {
    if (b++) f << ", ";
    f << x.top();
    x.pop();
  }
  return f << ']';
}
mt19937 rng(chrono::high_resolution_clock::now().time_since_epoch().count());
uniform_int_distribution<int> uid(0, numeric_limits<int>::max());
const int inf = 0x3f3f3f3f;
const long long infl = 0x3f3f3f3f3f3f3f3f;
const int mod = 1000000007;
const int maxn = (int)1e5 + 3;
int a[maxn];
int b[maxn];
int mp[maxn];
int main() {
  ios_base::sync_with_stdio(0), cin.tie(0), cout.tie(0);
  int n;
  cin >> n;
  for (int i = 0; i < n; ++i) {
    cin >> a[i];
    mp[a[i]] = i + 1;
  }
  for (int i = 0; i < n; ++i) {
    cin >> b[i];
    b[i] = mp[b[i]];
  }
  int m = n + 1;
  int ans = 0;
  for (int i = n - 1; i >= 0; --i) {
    if (b[i] > m) {
      ++ans;
    } else {
      m = b[i];
    }
  }
  cout << ans << '\n';
  return 0;
}
