#ifdef NACHIA
#define _GLIBCXX_DEBUG
#else
// disable assert
#define NDEBUG
#endif
#include <iostream>
#include <string>
#include <vector>
#include <algorithm>
using namespace std;
using ll = long long;
const ll INF = 1ll << 60;
#define REP(i,n) for(ll i=0; i<ll(n); i++)
template <class T> using V = vector<T>;
template <class A, class B> void chmax(A& l, const B& r){ if(l < r) l = r; }
template <class A, class B> void chmin(A& l, const B& r){ if(r < l) l = r; }


void testcase(){
  ll L, R; cin >> L >> R;
  ll msb = 1;
  while(msb * 2 <= R) msb *= 2;
  if(L & msb){ cout << "-1\n"; return; }
  ll ans = msb * (msb - 1);
  cout << ans << "\n";
}

int main(){
  cin.tie(0)->sync_with_stdio(0);
  ll T; cin >> T; REP(t,T)
  testcase();
  return 0;
}