#include <bits/stdc++.h>
using namespace std;
int power(int x, int y, int p) {
  int res = 1;
  x = x % p;
  while (y > 0) {
    if (y & 1) res = (res * x) % p;
    y = y >> 1;
    x = (x * x) % p;
  }
  return res;
}
int logN(int base, int num) {
  if (base == 1 && num != 1) return -1;
  if (num / base == 0) return 0;
  return 1 + logN(base, num / base);
}
bool isPrime(long long n) {
  if (n <= 1) return false;
  if (n <= 3) return true;
  if (n % 2 == 0 || n % 3 == 0) return false;
  for (int i = 5; i * i <= n; i = i + 6)
    if (n % i == 0 || n % (i + 2) == 0) return false;
  return true;
}
bool perfect(long long n) {
  return (long long)sqrt(n) * (long long)sqrt(n) == n ? true : false;
}
bool sortcol(const vector<int>& v1, const vector<int>& v2) {
  return v1[0] < v2[0];
}
int main() {
  int t, n;
  cin >> t;
  while (t--) {
    cin >> n;
    int pos = 1, arr[n], ans[n], flag[n + 1];
    vector<int> v;
    for (int i = 0; i < (n); i++) cin >> arr[i], flag[i + 1] = 1;
    for (int i = n; i >= 1; i--) v.push_back(i);
    for (int i = 0; i < (n); i++) {
      if (i > 0 && arr[i] == arr[i - 1]) {
        while (!v.empty() && !flag[v.back()]) v.pop_back();
        if (v.empty() || v.back() > arr[i]) {
          pos = 0;
          break;
        } else {
          ans[i] = v.back();
          v.pop_back();
        }
      } else
        ans[i] = arr[i], flag[arr[i]] = 0;
    }
    if (pos)
      for (int i = 0; i < (n); i++) cout << ans[i] << ' ';
    else
      cout << -1;
    cout << "\n";
  }
  return 0;
}
