#include <iostream>
#include <cstdio>
#include <queue>
#include <math.h>
#include <map>
#include <cstring>
#include <algorithm>
using namespace std;
typedef long long ll;
typedef long long ll;
const int maxn = 4e6 + 7;
const int mod = 1e9 + 7;
int n , k , m;
int T;
ll a ,b;
int main() {
    cin>>T;
    while(T--){
        cin>>a>>b;
        ll c = abs(a - b);
        ll d = c;
        if(c == 1){
            printf ("-1 -1\n");
            continue;
        }
        if(a == b){
            if(a == 1) printf ("-1 -1\n");
            else printf ("%d %d\n",2 , a);
            continue;
        }

        for(int i = 2; i * i <= c; i ++){
            if(c % i == 0){
                d = i;
                break;
            }
        }
        cout<<d<<" "<<c<<endl;
    }




    return 0;
}