#include <bits/stdc++.h>
using namespace std;
int main ()
{
    int t;
    cin>>t;
    while(t--){
        long long a,b;
        cin>>a>>b;
        long long m2 = min(a,b);
        int m1 = -1; 
        if(a<b)swap(a,b);
        long long k = a-b;
        if(k==1){
            cout<<"-1 -1"<<endl;
            continue;        
        }
        if(a==b){
            if(a==1){
                cout<<"-1 -1"<<endl;
                continue;
            }
            cout<<"2 "<<a<<endl;
            continue;
        }
        
        for(int i = 2;i*i<=k;i++){
            if(k%i==0){
                m1 = i;
                break;
            }
            
        }
        
        if(m1==-1)m1=k;
        cout<<m1<<" "<<k<<endl;
        
    }
    
    
    
    
    return 0;
}