#include <bits/stdc++.h>
using namespace std;
using LL = long long;
int main() {
  LL x, s;
  cin >> x >> s;
  LL d = s - x;
  if (d >= 0 && d % 2 == 0) {
    int K = 60;
    vector<int> c(K, 0);
    for (int j = 1; j < K; ++j) {
      if (d & ((LL)1 << j)) {
        c[j - 1] += 2;
      }
    }
    for (int j = 0; j < K; ++j) {
      if (x & ((LL)1 << j)) {
        c[j] += 1;
      }
    }
    vector<LL> ans;
    while (true) {
      LL y = 0;
      for (int j = 0; j < K; ++j) {
        if (c[j] > 0) {
          y |= ((LL)1 << j);
          --c[j];
        }
      }
      if (y == 0) {
        break;
      } else {
        ans.push_back(y);
      }
    }
    cout << ans.size() << '\n';
    for (int j = 0; j < ans.size(); ++j) {
      cout << ans[j] << ((j == ans.size() - 1) ? '\n' : ' ');
    }
  } else {
    cout << "-1\n";
  }
  return 0;
}
