#include<bits/stdc++.h>
#define ll long long
#define uint unsigned int
#define ull unsigned long long
#define inf 1010000000
#define infll 1010000000000000000ll
#define vi vector<int>
#define vll vector<ll>
#define pb push_back
#define pii pair<int,int>
#define pll pair<ll,ll>
#define pdd pair<double,double>
#define mpr make_pair
#define fi first
#define se second
#define pq priority_queue<int>
#define pqll priority_queue<ll>
#define up(x,y) (x<(y)?x=(y):0)
#define dn(x,y) (x>(y)?x=(y):0)
#define ad(x,y) (x=(x+(y))%mod)
#define cbn(x,y) ((ll)fac[x]*inv[y]%mod*inv[(x)-(y)]%mod)
using namespace std;

int read(); ll readll();

int main(){
    int cas = read();
    while (cas--){
        int x = read(), y = read();
        if (x > y) swap(x, y);
        if (x == y){
            if (y == 1){ puts("-1 -1"); continue; }
            printf("%d %d\n", 2, y); continue;
        } else y -= x;
        if (y == 1){ puts("-1 -1"); continue; }
        int t = 2;
        for (; t * t <= y; t++) if (!(y%t)) break;
        if (t * t <= y) printf("%d %d\n", t, y);
        else printf("%d %d\n", y, y); 
    }
    return 0;
}

int read(){
    int x=0; char ch=getchar(); bool flag=0;
    while (ch<'0' || ch>'9'){ if (ch=='-') flag=1; ch=getchar(); }
    while (ch>='0' && ch<='9'){ x=x*10+ch-'0'; ch=getchar(); }
    return flag?-x:x;
}
ll readll(){
    ll x=0; char ch=getchar(); bool flag=0;
    while (ch<'0' || ch>'9'){ if (ch=='-') flag=1; ch=getchar(); }
    while (ch>='0' && ch<='9'){ x=x*10+ch-'0'; ch=getchar(); }
    return flag?-x:x;
}