#include <bits/stdc++.h>
using namespace std;
int main() {
  int t;
  cin >> t;
  while (t--) {
    int n;
    cin >> n;
    int r = n - 1;
    vector<int> v;
    int q;
    int m = 0;
    cin >> q;
    v.push_back(q);
    set<int> s;
    s.insert(q);
    int i = 1;
    int l = q;
    while (r--) {
      cin >> q;
      if (q == l) {
        int b = 0;
        for (; i <= n; i++) {
          if (s.find(i) == s.end() && i < q) {
            b = 1;
            v.push_back(i);
            s.insert(i);
            break;
          }
        }
        if (b == 0) {
          m = 1;
        }
      } else if (q > l) {
        s.insert(q);
        v.push_back(q);
      } else {
        m = 1;
      }
      l = q;
    }
    if (m == 1 && n > 1)
      cout << -1 << endl;
    else if (m == 0) {
      for (int i = 0; i < n; i++) {
        cout << v[i] << " ";
      }
      cout << endl;
    }
  }
}
