#include <bits/stdc++.h>
using namespace std;
int main() {
  ios::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  int t;
  cin >> t;
  for (int i = 0; i < t; i++) {
    int n;
    cin >> n;
    vector<int> p(n), result;
    for (int& j : p) {
      cin >> j;
    }
    vector<int> maximums;
    vector<bool> used(n, false);
    result.push_back(p[0]);
    used[p[0] - 1] = true;
    int idx = 0;
    for (idx; idx < p[0] - 1; idx++) {
      maximums.push_back(idx + 1);
    }
    idx++;
    for (int j = 1; j < n; j++) {
      if (p[j] > p[j - 1]) {
        result.push_back(p[j]);
        used[p[j] - 1] = true;
        for (idx; idx < p[j] - 1; idx++) {
          if (!used[idx]) maximums.push_back(idx + 1);
        }
        idx++;
      } else {
        if (maximums.size() > 0) {
          used[maximums[maximums.size() - 1] - 1] = true;
          result.push_back(maximums[maximums.size() - 1]);
          maximums.pop_back();
        }
      }
    }
    if (result.size() < n)
      cout << -1 << endl;
    else {
      for (int& i : result) {
        cout << i << ' ';
      }
      cout << endl;
    }
  }
}
