#include<bits/stdc++.h>
#define ll long long
#define ull unsigned long long
#define For(i,j,k) for (int i=(int)(j);i<=(int)(k);i++)
#define Rep(i,j,k) for (int i=(int)(j);i>=(int)(k);i--)
using namespace std;

void solve(){
    int a,b;
    scanf("%d%d",&a,&b);
    if (a==b){
        if (a==1) puts("-1 -1");
        else printf("%d %d\n",2,a);
    }
    else{
        int d=abs(b-a);
        if (d==1) puts("-1 -1");
        else{
            for (int i=2;i*i<=d;i++){
                if (d%i==0){
                    printf("%d %d\n",i,d);
                    return;
                }
            }
            printf("%d %d\n",d,d);
        }
    }
}
int main(){
    int T;
    scanf("%d",&T);
    while (T--) solve();
}