#include <bits/stdc++.h>

using namespace std;
using LL = long long;

int main()
{
    ios::sync_with_stdio(false);
    cin.tie(0);
    int T;
    cin >> T;
    while (T--)
    {
        LL a, b;
        cin >> a >> b;
        if (a > b)
            swap(a, b);
        LL d = b - a;
        if (d == 0)
        {
            if (a == 1)
                cout << "-1 -1" << std::endl;
            else
            {
                cout << "2 " << a << std::endl;
            }
        }
        else if (d == 1)
        {
            cout << "-1 -1" << std::endl;
        }
        else
        {
            LL x = d;
            if (d % 2 == 0)
                x = 2;
            else
            {
                for (LL i = 3; i * i <= d; ++i)
                {
                    if (d % i == 0)
                    {
                        x = i;
                        break;
                    }
                }
            }
            cout << x << " " << d << std::endl;
        }
    }
    return 0;
}