#include <bits/stdc++.h>   using namespace std;   int main() {     ios::sync_with_stdio(0);     cin.tie(0);     cout.tie(0);     int t = 1;     while (t--) {       int sum, limit;       cin >> sum >> limit;       vector<pair<int, int>> v;       for (int i = 1; i <= limit; i++) {         v.push_back({1 << __builtin_ctz(i), i});       }       sort(v.rbegin(), v.rend());       vector<int> a;       int i = 0;       while (sum) {         if (i == v.size()) break;         if (sum >= v[i].first) {           a.push_back(v[i].second);           sum -= v[i].first;         }         i++;       }       if (sum != 0)         cout <<  -1 n ;       else {         cout << a.size() <<   n ;         for (auto i : a) {           cout << i <<    ;         }         cout <<   n ;       }     }     return 0;   }   