#include<bits/stdc++.h>
using namespace std;



int main() {
    int T;
    long long a,b;

    cin>>T;
    while (T--) {
        cin>>a>>b;

        if (abs(a-b)==1 || a+b==2)
            cout<<-1<<" "<<-1<<endl;
        else if (a==b)
            cout<<2<<" "<<a<<endl;
        else {
            long long d=abs(a-b);
            long long i;
            for (i=2;i*i<=d;i++)
                if (!(d%i))
                    break;
            if (i*i<=d)
                cout<<i<<" "<<d<<endl;
            else
                cout<<d<<" "<<d<<endl;
        }
    }
    

    return 0;
}