#include <bits/stdc++.h>
using namespace std;
const long long M = 998244353;
const long long N = 2e6 + 10;
const long long IM = 1e15 + 37;
const long double PI = 3.1415926535897932384;
inline void PP(long long n) { cout << n << " "; }
void PV(vector<long long> v) {
  for (long long i = 0; i < v.size(); i++) cout << v[i] << " ";
  cout << "\n";
}
void PVV(vector<pair<long long, long long> > v) {
  for (long long i = 0; i < v.size(); i++)
    cout << v[i].first << " " << v[i].second << "\n";
}
void PA(long long v[], long long n, long long x = 0) {
  for (long long i = x; i < n + x; i++) cout << v[i] << ' ';
  cout << "\n";
}
void IN(long long a[], long long n, long long x = 0) {
  for (long long i = x; i < n + x; i++) cin >> a[i];
}
inline void op() {}
signed main() {
  op();
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  cout.tie(NULL);
  long long t;
  cin >> t;
  while (t--) {
    long long l, r;
    cin >> l >> r;
    if (l + l > r) {
      PV({-1, -1});
    } else
      PV({l, l + l});
  }
  return 0;
}
