#include <bits/stdc++.h>
using namespace std;
const int inf = 1e9;
int T, a, b;
int main() {
    scanf("%d", &T);
    while (T--) {
        scanf("%d%d", &a, &b);
        int w = abs(a - b);
        if (w == 0) {
            if (max(a, b) == 1) printf("-1 -1\n");
            else printf("%d %d\n", 2, max(a, b));
        } else if (w == 1) printf("-1 -1\n");
        else {
            int mn = w, mx = w;
            for (int i = 2; i * i <= w; ++i)
                if (w % i == 0) {
                    mn = i; break;
                }
            printf("%d %d\n", mn, mx);
        }
    }
}