#include <cstdio>
#include <cmath>

int main() {
    int Tests;
    scanf("%d", &Tests);
    while (Tests--) {
        int a, b;
        scanf("%d%d", &a, &b);
        int x = std::abs(a - b);
        if (x == 0) {
            if (a == 1)
                puts("-1 -1");
            else
                printf("%d %d\n", 2, a);
        } else if (x == 1)
            puts("-1 -1");
        else {
            int p = x;
            for (int y = 2; y * y <= x; ++y)
                if (x % y == 0) {
                    p = y;
                    break;
                }
            printf("%d %d\n", p, x);
        }
    }
    return 0;
}