#include <iostream>

using namespace std;

int main()
{
    int T;
    cin>> T;
    while(T--) {
        int a, b;
        cin>> a>>b;
        if(a < b)
            swap(a,b);
        if (a==1)
            printf("-1 -1\n");
        else if(a - b == 0)
            printf("%d %d\n", 2, a);
        else if(a - b == 1)
            printf("-1 -1\n");
        else {
            int sub = a - b;
            int min_num = sub;
            for (int i=2;i*i <=sub; i++)
                if ((sub %i) ==0 )
            {
                 min_num = i;
                 break;

            }
            printf("%d %d\n", min_num, sub);
        }
    }
    return 0;
}