code2162C.cpp

/*
 * Contest : Codeforces
 * Problem : 2162C - Beautiful XOR
 * Link    : https://codeforces.com/contest/2162/problem/C
 */

#include <bits/stdc++.h>
using namespace std;
using ll = long long;

#define fastio ios::sync_with_stdio(0); cin.tie(0);

void solve() {
  cerr << '\n';
  ll a, b;
  cin >> a >> b;

  if (a == b) {
    cout << "0\n";
    return;
  }
  if ((ll)log2(b) > (ll)log2(a)) {
    cout << "-1\n";
    return;
  }
  vector<ll> ans;
  while (a != b) {
    ll x = 0;

    for (int i = 0; i <= a; i++) {
      ll y = (1 << i);
      if (x + y > a) break;

      // bit i of B should be on
      if (b & y) {
        // bit i of A is off => add bit i
        if (!(a & y)) x += y;
      }
      // bit i is off
      else {
        // bit i of A is on => add bit i
        if (a & y) x += y;
      }
    }
    ans.push_back(x);
    a = a ^ x;
  }

  cout << (int)ans.size() << '\n';
  for (auto &i : ans) cout << i << ' ';
  cout << '\n';
}

int main() {
  fastio

  int tc; cin >> tc;
  while (tc--) solve();

  return 0;
}