#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
ll t = 1,n,m,k,q,l,r,a,b,c,u,v,x,y,z,mod = 1e9 + 7;
string s;
struct st{ll x,y; /*bool operator < (const st &a) const{return x < a.x;};*/};
bool cmp(const st &a,const st &b){return a.x < b.x;}
inline ll read(){
    ll s = 0,w = 1;
    char ch = getchar();
    while (ch > '9' || ch < '0'){ if (ch == '-') w = -1; ch = getchar();}
    while (ch <= '9' && ch >= '0') s = (s << 1) + (s << 3) + (ch ^ 48),ch = getchar();
    return s * w;
}
ll qp(ll x,ll y){
    ll a = 1,b = x;
    while (y){
        if (y & 1) a = a * b % mod;
        b = b * b % mod,y >>= 1;
    }
    return a;
}
ll get(ll x){
    for (ll i = 2;i <= sqrt(x);i += 1) if (!(x % i)) return i;
    return x;
}
int main(){t = read();
while (t --){
    n = read(),m = read();
    ll qwq = abs(n - m);
    if (n == 1 && m == 1) printf("%lld %lld\n",-1ll,-1ll);
    else if (!qwq) printf("%lld %lld\n",2ll,n);
    else if (qwq == 1) printf("%lld %lld\n",-1ll,-1ll);
    else printf("%lld %lld\n",get(qwq),qwq);
}
    return 0;
}