#include <bits/stdc++.h>
using namespace std;
int main() {
  int t;
  cin >> t;
  while (t--) {
    long long int l, r;
    cin >> l >> r;
    if (l * 2 <= r)
      cout << l << " " << l * 2 << endl;
    else
      cout << -1 << " " << -1 << endl;
  }
  return 0;
}
