#include<iostream>
using namespace std;
using ll = long long;

int main(){
    int T;
    cin >> T;
    for(int testcase = 0; testcase < T; testcase++){
        ll L,R;
        cin >> L >> R;
        ll a = 0, b = 0;
        for(ll bit = 32; bit >= 0; bit--){
            if(R >= (1ll<<bit)){
                if(a==0)a += (1ll<<bit);
                else b += (1ll<<bit);
            }
        }
        if(b >= L)cout << a*b << endl;
        else cout << -1 << endl;
    }
    return 0;
}