CF 250B

#include <algorithm>
#include <bitset>
#include <deque>
#include <cmath>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <iostream>
#include <list>
#include <map>
#include <queue>
#include <set>
#include <sstream>
#include <stack>
#include <string>
#include <utility>
#include <vector>

#define fst first
#define snd second
#define all(x) (x).begin(), (x).end()
#define clr(a, v) memset(a, v, sizeof(a))
#define pb push_back
#define mp make_pair
#define sz(x) (int)(x.size())
#define FORN(i,s,n) for(int i=s;i<(int)(n);i++)
#define FOR(i,n) FORN(i,0,n)
#define FORIT(i,x) for( typeof x.begin()  i=x.begin(); i!=x.end(); i++ )
#define trace(x)    cerr << #x << ": " << x << endl;
#define trace2(x, y) cerr << #x << ": " << x << " | " << #y << ": " << y << endl;

using namespace std;

typedef long long int64;
typedef vector <int> vi;
typedef pair <int,int> ii;
typedef vector <string> vs;
typedef vector <ii> vii;

const int INF = 2e9+9;

int main(){
    int sum, lim;
    cin>>sum>>lim;
    int acm[lim+1];
    priority_queue< ii > PQ;
    acm[0]=0;
    FORN(i,1,lim+1){
        acm[i]=acm[i-1]+( i&-i );
        PQ.push ( mp(i&-i,i) );
    }
    if (acm[lim]<sum) cout<<-1<<endl;
    else{
        vi ans;
        int diff=acm[lim]-sum;
        while(!PQ.empty()){
            ii a=PQ.top(); PQ.pop();\
            if (diff-a.fst>=0) diff-=a.fst;
            else ans.pb(a.snd);
        }
        if(diff>0) cout<<-1<<endl;
        else{
            cout<<sz(ans)<<endl;
            FOR(i,sz(ans)) cout<<ans[i]<<" ";
            cout<<endl;
        }
    }
}