#include<iostream>
#include<cstdio>
using namespace std;
int main(){
    int T;
    long long a, b, c, d;
    cin>>T;
    while(T--){
        scanf("%lld%lld",&a,&b);
        if(a > b) swap(a, b);
        long long c = b - a;
        if(b<2) puts("-1 -1");
        else if(!c) printf("2 %lld\n", a);
        else if(c < 2)puts("-1 -1");
        else{
            for(d = 2; d*d <= c; d++){
                if(c % d == 0)break;
            }
            if(c%d == 0)
                printf("%lld %lld\n", d, c);
            else printf("%lld %lld\n", c, c);
        }
    }
}