#include<bits/stdc++.h>
using namespace std;

#define Mod(x) (x>=P)&&(x-=P)
#define rep(i,a,b) for(ll i=a,i##end=b;i<=i##end;++i)
#define drep(i,a,b) for(ll i=a,i##end=b;i>=i##end;--i)
#define erep(i,a,b) for(ll i=hd[a];i;i=nxt[i])

typedef long long ll;
void Max(ll &x,ll y){x<y&&(x=y);}
void Min(ll &x,ll y){x>y&&(x=y);}

bool vio;
char IO;
ll rd(ll res=0){
    bool f=0;
    while(IO=getchar(),IO<48||IO>57)
        f|=IO=='-';
    do res=(res<<1)+(res<<3)+(IO^48);
    while(IO=getchar(),isdigit(IO));
    return f?-res:res;
}
const ll M=1e6+10,P=998244353;
ll q[M];
bool let;
int main(){
    //cerr<<(&vio-&let)/1024.0/1024<<endl;
    rep(cas,1,rd()){
        ll a=rd(),b=rd();
        ll t=abs(a-b),tot=0;
        if(a==b){
            if(a==1)cout<<-1<<" "<<-1<<endl;
            else cout<<2<<" "<<a<<endl;
            continue;
        }
        rep(i,1,sqrt(t)){
            if(t%i==0){
                q[++tot]=i;
                q[++tot]=t/i;
            }
        }
        ll ans1=-1,ans2=-1;
        rep(i,1,tot)if(q[i]!=1&&a%q[i]==b%q[i]){
            if(ans1==-1)ans1=ans2=q[i];
            else {
                Max(ans2,q[i]);
                Min(ans1,q[i]);
            }
        }
        cout<<ans1<<" "<<ans2<<endl;
    }
}