//#include <bits/stdc++.h>
#include <iostream>
#include <iomanip>
#include <math.h>
#include <cmath>
#include <algorithm>
#include <climits>
#include <functional>
#include <cstring>
#include <string>
#include <cstdlib>
#include <ctime>
#include <cstdio>
#include <vector>
#include <stack>
#include <queue>
#include <deque>
#include <map>
#include <set>
#include <bitset>
#include <complex>
//#include <ext/pb_ds/assoc_container.hpp>
//#include <ext/pb_ds/tree_policy.hpp>
#define itn int
#define nit int
#define ll long long
#define ms multiset
#define F(i,a,b) for(register int i=a,i##end=b;i<=i##end;++i)
#define UF(i,a,b) for(register int i=a,i##end=b;i>=i##end;--i)
#define re register
#define ri re int
#define il inline
#define pii pair<int,int>
#define cp complex<double>
//#pra gma G CC opti mize(3)
using namespace std;
using std::bitset;
//using namespace __gnu_pbds;
const double Pi=acos(-1);
namespace fastIO {
    template<class T>
    inline void read(T &x) {
        x=0;
        bool fu=0;
        char ch=0;
        while(ch>'9'||ch<'0') {
            ch=getchar();
            if(ch=='-')fu=1;
        }
        while(ch<='9'&&ch>='0') x=(x*10-48+ch),ch=getchar();
        if(fu)x=-x;
    }
    inline int read() {
        int x=0;
        bool fu=0;
        char ch=0;
        while(ch>'9'||ch<'0') {
            ch=getchar();
            if(ch=='-')fu=1;
        }
        while(ch<='9'&&ch>='0') x=(x*10-48+ch),ch=getchar();
        return fu?-x:x;
    }
    template<class T,class... Args>
    inline void read(T& t,Args&... args) {
        read(t);
        read(args...);
    }
    char _n_u_m_[40];
    template<class T>
    inline void write(T x ) {
        if(x==0){
            putchar('0');
            return;
        }
        T tmp = x > 0 ? x : -x ;
        if( x < 0 ) putchar('-') ;
        register int cnt = 0 ;
        while( tmp > 0 ) {
            _n_u_m_[ cnt ++ ] = tmp % 10 + '0' ;
            tmp /= 10 ;
        }
        while( cnt > 0 ) putchar(_n_u_m_[ -- cnt ]) ;
    }
    template<class T>
    inline void write(T x ,char ch) {
        write(x);
        putchar(ch);
    }
}
using namespace fastIO;
int a,b,c;
inline int fac(int x){
    F(i,2,sqrt(x))if(x%i==0)return i;return x;
}
int main() {
    F(asdfa,1,read()){
        read(a);read(b);
        if(a==1&&b==1){
            puts("-1 -1");
        }else{
        c=max(a,b)-min(a,b);
        if(!c)write(2,' '),write(a,'\n');
        else if(c==1)puts("-1 -1");
        else{
            write(fac(c),' ');write(c,'\n');
        }}
    }
    return 0;
}