#include <bits/stdc++.h>

using namespace std;

typedef long long ll;

const int N = 1e5+10, mod = 1e9+7;

int main() {
    ios::sync_with_stdio(0);
    cin.tie(0), cout.tie(0);
    int t;
    cin>>t;
    while(t--) {
        ll a, b;
        cin>>a>>b;
        if(a < b) swap(a, b);
        if(a == b) {
            if(a > 1)
                cout<<2<<" "<<a<<endl;
            else
                cout<<-1<<" "<<-1<<endl;
        } else if(a - b == 1) {
            cout<<-1<<" "<<-1<<endl;
        } else {
            ll mn = a - b, mx = mn;
            ll n = sqrt(mx);
            for(int i = 2; i <= n; i++) {
                if(mx % i == 0) {
                    mn = i;
                    break;
                }
            }
            cout<<mn<<" "<<mx<<endl;
        }
    } 
    return 0;
}