#include <bits/stdc++.h>
using namespace std;
 
#define co(n) cout<<n<<endl;
const double eps=1e-10,pi=3.1415926535898;
const int mod=1e9+7,maxn=4e5+10;
int T,n,m,k,x,y,a[maxn],b[maxn];
 
int main(int argc, char const *argv[]) {
    //init();
    T = 1;
    scanf("%d", &T);
    for (int _=1;_<=T;++_) {
        long long ans=0;
        scanf("%d %d", &n, &m);
        k = max(n, m) - min(n, m);
        if (n == m) {
            if (n == 1) printf("-1 -1\n");
            else printf("2 %d\n", n);
            continue;
        }
        if (k == 1) {
            printf("-1 -1\n");
            continue;
        }
        int flag=1;
        for (int i=2;i*i<=k;++i) {
            if (k%i == 0) {
                printf("%d %d\n", i, k);
                flag = 0;
                break;
                
            }
        }
        if (flag) printf("%d %d\n", k, k);
    }
    return 0;
}