#include <bits/stdc++.h>

using namespace std;
typedef long long ll;
typedef pair<int, int> pii;

void solve() {
    int a, b;
    scanf("%d%d", &a, &b);
    if (a == b) {
        if (a == 1) printf("-1 -1\n");
        else printf("2 %d\n", a);
    } else {
        int c = abs(a - b);
        if (c == 1) {
            printf("-1 -1\n");
            return ;
        }
        for (int i = 2; i * i <= c; i++) {
            if (c % i == 0) { printf("%d %d\n", i, c); return ; }
        }
        printf("%d %d\n", c, c);
    }
}

int main() {
    int T = 0;
    scanf("%d", &T);
    while (T--) solve();

    return 0;
}