#include <bits/stdc++.h>
using namespace std;
long long int bnm(long long int n, long long int k) {
  long long int res = 1;
  if (n < k) return 0;
  if (k > n - k) k = n - k;
  for (long long int i = 0; i < k; ++i) {
    res *= (n - i);
    res /= (i + 1);
  }
  return res;
}
long long int gcd(long long int a, long long int b) {
  if (a == 0) return b;
  return gcd(b % a, a);
}
bool isPrime(int 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;
}
long long int power(long long int base, long long int exp) {
  long long int res = 1;
  while (exp > 0) {
    if (exp % 2 == 1) res = (res * base) % 1000000007;
    base = (base * base) % 1000000007;
    exp /= 2;
  }
  return res % 1000000007;
}
long long int str(string s, char e) {
  for (long long int i = s.size() - 1; i >= 0; i--) {
    if (s[i] == e) return i;
  }
}
void ghost() {
  long long int n, i, k = 0, f = 0, g = 0, e = 0, u = 0, d = 0, q = 0, l = 0,
                      y = 0, s = 0, x = 0;
  cin >> q;
  while (q--) {
    queue<long long int> z;
    cin >> n;
    l = 0;
    long long int a[n + 1], b[n + 1], c[n + 1];
    for (long long int i = 1; i < n + 1; i++) a[i] = 0;
    for (long long int i = 1; i < n + 1; i++) c[i] = 1;
    b[0] = 0;
    a[0] = 0;
    for (long long int i = 1; i < n + 1; i++) {
      cin >> b[i];
    }
    for (long long int i = 1; i < n + 1; i++) {
      if (b[i] != b[i - 1]) {
        a[i] = b[i];
        c[b[i]]--;
      }
    }
    for (long long int i = 1; i < n + 1; i++) {
      if (c[i] == 1) z.push(i);
    }
    for (long long int i = 1; i < n + 1; i++) {
      if (a[i] == 0) {
        a[i] = z.front();
        z.pop();
      }
    }
    d = a[0];
    for (long long int i = 1; i < n + 1; i++) {
      if (max(d, a[i]) != b[i]) {
        cout << "-1" << endl;
        l = 1;
        break;
      }
      f = max(a[i], a[i - 1]);
      d = max(f, d);
    }
    if (l != 1) {
      for (long long int i = 1; i < n + 1; i++) cout << a[i] << " ";
      cout << endl;
    }
  }
}
signed main() {
  int test = 1;
  ios_base::sync_with_stdio(false);
  cin.tie(0);
  cout.tie(0);
  while (test--) ghost();
  return 0;
}
