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