#include<cstdio>
#include<cstring>
#include<algorithm>
using namespace std;
int T,a,b;
int abs(int x){return x<0?-x:x;}
int main()
{
    scanf("%d",&T);
    while(T--)
    {
        scanf("%d%d",&a,&b);
        if(a==1&&b==1){puts("-1 -1");continue;}
        int x=abs(a-b);
        if(x==1){puts("-1 -1");continue;}
        if(a==b){printf("2 %d\n",a);continue;}
        bool flag=true;
        for(int i=2;i*i<=x;i++)
            if(x%i==0)
            {
                printf("%d %d\n",i,x);
                flag=false;
                break;
            }
        if(flag==true) printf("%d %d\n",x,x);
    }
    return 0;
}