func_code_string: #include <bits/stdc++.h>   using namespace std;   using ll = long long;   using pii = pair<int, int>;   const double PI = 4 * atan(1);   const int INF = 0x3f3f3f3f;   const ll LINF = 0x3f3f3f3f3f3f3f3f;   const int MOD = 1e9 + 7;   const int MAX_N = 2e6 + 10;   int n;   int a[MAX_N], b[MAX_N], p[MAX_N];   void solve() {     for (int i = 1; i <= n; ++i) {       p[b[i]] = i;     }     if (p[1]) {       int i = 2;       for (; p[i] == p[1] + i - 1; ++i)         ;       if (p[i - 1] == n) {         int j;         for (j = i; j <= n && p[j] <= j - i; ++j)           ;         if (j > n) {           cout << n - i + 1 <<   n ;           return;         }       }     }     int ans = 0;     for (int i = 1; i <= n; ++i) ans = max(ans, p[i] - i + 1 + n);     cout << ans <<   n ;   }   int main() {     cin >> n;     for (int i = 1; i <= n; ++i) cin >> a[i];     for (int i = 1; i <= n; ++i) cin >> b[i];     solve();     return 0;   }   