func_code_string: #include <bits/stdc++.h>   using namespace std;   const int maxn = (3e5) + 10, mod = 1e9 + 7;   int n, a[maxn];   map<int, int> mark;   int32_t main() {     ios::sync_with_stdio(false);     cin.tie(NULL);     cout.tie(NULL);     cin >> n;     for (int i = 0; i < n; i++) cin >> a[i];     int ans = 0;     int num = 0;     for (int i = 0; i < n; i++) {       if (a[i] > num) return cout << i + 1 << endl, 0;       if (a[i] == num) num++;     }     cout << -1 << endl;     return 0;   }   