Balanced Tunnel

  #include <bits/stdc++.h>
  using namespace std;

  #define cin(vec) for(auto& i : vec) cin >> i
  #define cin_2d(vec, n, m) for(int i = 0; i < n; i++) for(int j = 0; j < m && cin >> vec[i][j]; j++);
  #define cout(vec) for(auto& i : vec) cout << i << " "; cout << "\n";
  #define cout_2d(vec, n, m) for(int i = 0; i < n; i++, cout << "\n") for(int j = 0; j < m && cout << Matrix[i][j] << " "; j++);
  #define cout_map(mp) for(auto& [f, s] : mp) cout << f << "  " << s << "\n";
  #define loop(a, b, c) for(int i = a ; i < (b); i += c)
  #define fixed(n) cout << fixed << setprecision(n);
  #define ceil(n, m) (((n) / (m)) + ((n) % (m) ? 1 : 0))
  #define fill(vec, value) memset(vec, value, sizeof(vec));
  #define all(vec) vec.begin(),vec.end()
  #define rall(vec) vec.rbegin(),vec.rend()
  #define sz size()
  #define fi first
  #define se second
  #define Pair pair <int,int>
  #define ll long long
  #define ull unsigned long long
  #define Mod  1'000'000'007
  #define INF 2'000'000'000
  #define PI acos(-1)

  void Code_Crush(){
    ios_base::sync_with_stdio(false);   cin.tie(nullptr);   cout.tie(nullptr);
    #ifndef ONLINE_JUDGE
      freopen("input.txt", "r", stdin), freopen("output.txt", "w", stdout);
    #endif
  }

  int main(){
      Code_Crush();
      ll n, counter = 0;                   cin >> n;
      vector < int > before(n), after(n);
      vector < int > vis(n + 1);
      cin(before);
      cin(after);
      for(int l = n - 1, r = n - 1; r >= 0 && l >= 0;){
          if(before[r] != after[l] && !vis[after[l]]) vis[before[r]] = true, r--, counter++;
          else if(after[r] != after[l] && vis[after[l]]) l--;
          else r--, l--;
      }
      cout << counter;
      return 0;
  }