func_code_string: #include <bits/stdc++.h>   using namespace std;   int main() {     int t;     cin >> t;     for (int e = 0; e < t; e++) {       long long n;       cin >> n;       vector<bool> used(n + 2, false);       long long q;       long long last = -1;       vector<long long> ans;       long long index = 1;       for (int i = 0; i < n; i++) {         cin >> q;         if (q != last) {           ans.push_back(q);           last = q;           used[q] = true;           continue;         }         while (used[index]) {           index++;           if (index >= q) {             index = -1;             break;           }         }         if (index == -1) {           cout << -1 << endl;           while (i < n - 1) {             cin >> q;             i++;           }           break;         }         ans.push_back(index);         used[index] = true;         continue;       }       if (index != -1)         for (int i = 0; i < ans.size(); i++) {           cout << ans[i] <<    ;         }       cout << endl;     }   }   