#include <bits/stdc++.h>
using namespace std;
int main() {
  ios::sync_with_stdio(false);
  cout.tie(0);
  int n;
  cin >> n;
  vector<bool> in(n + 1);
  for (int i = 0; i < n; i++) {
    int a;
    cin >> a;
    in[a] = true;
  }
  vector<int> b(n);
  for (int i = 0; i < n; i++) {
    cin >> b[i];
  }
  int ind = 0;
  int next_ = 1;
  vector<int> c = b;
  for (; next_ <= n; ind++) {
    int t = ind - n - 1;
    if (t >= 0 && t < n) {
      in[b[ind - n - 1]] = true;
    }
    if (c[ind % n] == next_) {
      next_++;
      c[ind % n] = -1;
      continue;
    }
    if (c[ind % n] == -1 && in[next_]) {
      next_++;
      continue;
    }
    c[ind % n] = -1;
    if (ind - next_ + 1 < n) {
      next_ = 1;
    }
  }
  cout << ind - n << endl;
}
