#include <bits/stdc++.h>
using namespace std;
int a, b, T;
int main() {
    scanf("%d", &T);
    while (T--) {
        scanf("%d%d", &a, &b);
        if (a == b) {
            if (a == 1) puts("-1 -1");
            else printf("%d %d\n", 2, a);
            continue;
        }
        int d = abs(a - b);
        if (d == 1) {
            puts("-1 -1");
            continue;
        }
        int ok = 0;
        for (int i = 2; i * i <= d; i++) {
            if (d % i == 0) {
                printf("%d %d\n", i, d);
                ok = 1;
                break;
            }
        }
        if (ok == 0) printf("%d %d\n", d, d);
    }
}