#include <bits/stdc++.h>
using namespace std;
const int N = 1e6 + 1;
int a[N], b[N], ans[N];
int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  int t, n;
  cin >> t;
  while (t--) {
    cin >> n;
    for (int i = 0; i < (int)n; i++) cin >> a[i], b[i + 1] = 0;
    int mn = 1;
    bool ok = 1;
    for (int i = 0; i < (int)n; i++) {
      if (!b[a[i]])
        ans[i] = a[i], b[a[i]] = 1;
      else if (mn < a[i])
        ans[i] = mn, b[mn] = 1, mn++;
      else
        ok = 0;
      while (b[mn] && mn <= n) mn++;
    }
    if (ok) {
      for (int i = 0; i < (int)n; i++) cout << ans[i] << " \n"[i == (int)n - 1];
      ;
    } else
      cout << "-1\n";
  }
}
