#include <cstdio>
#include <cstring>
#include <algorithm>
#include <iostream>
#include <ctime>
#include <cmath>
using namespace std;
int T,n,m;
int main(){
    scanf("%d",&T);
    for(int ii=1;ii<=T;++ii){
        scanf("%d%d",&n,&m);
        if(n < m)swap(n,m);
        int x = n-m;
        if(x == 0){
            if(n == 1)printf("-1 -1\n");
            else printf("%d %d\n",2, n);
        }else if(x == 1)printf("-1 -1\n");
        else{
            bool flag = false;
            int ans1,ans2;
            ans2 = x;
            for(int i=2;i*i <= x;++i){
                if((x % i) == 0){
                    flag = true;
                    ans1 = i;
                    break;
                }
            }
            if(!flag)ans1 = ans2;
            printf("%d %d\n", ans1, ans2);
        }
    }
    return 0;
}