#include<bits/stdc++.h>
#define LL long long
#define PII pair<int,int>
#define PLI pair<LL,int>
#define lson o<<1,l,mid
#define rson o<<1|1,mid+1,r
#define lowbit(x) (x&(-x))
using namespace std;

int T;
LL a,b;

int main(){
#ifdef OJ
    freopen("data.in","r",stdin);
    freopen("data.out","w",stdout);
#endif
    scanf("%d",&T);
    while(T--){
        scanf("%lld %lld",&a,&b);
        if(a==b){
            if(a>1) printf("2 %lld\n",a);
            else printf("-1 -1\n");
            continue;
        }
        if(abs(a-b)==1){
            printf("-1 -1\n");
            continue;
        }
        LL d=abs(a-b);
        LL t=sqrt(d),c=d;
        for(LL i=2;i<=t;i++){
            if(d%i==0){
                c=i;
                break;
            }
        }
        printf("%lld %lld\n",c,d);
    }
}