#include<bits/stdc++.h>
using namespace std;
const int maxn = 1e5+5;
const int mod=1e9+7;
#define ll long long
#define IOS ios::sync_with_stdio(false),cin.tie(0)
ll isp(ll n){
    for(ll i=2;i*i<=n;++i){
        if(n%i==0)
            return i;
    }
    return n;
}
int main(){
    IOS;
    int t;
    cin>>t;
    while(t--){
        ll a,b;
        cin>>a>>b;
        if(a>b)
            swap(a,b);
        ll c=b-a;
        if(c==1)
            cout<<-1<<" "<<-1<<"\n";
        else if(c==0){
            if(a==1)
                cout<<-1<<" "<<-1<<"\n";
            else
                cout<<2<<" "<<a<<"\n";
        }
        else{
            cout<<isp(c)<<" "<<c<<"\n";
        }
    }
    return 0;
}