#include <bits/stdc++.h>
#include <iostream>
#include <vector>
#include <algorithm>
#include <stack>
//#include <atcoder/all>
using namespace std;

#define reps(i, a, n) for (int i = (a); i < (int)(n); ++i)
#define rep(i, n) reps(i, 0, n)

#define ALL(x) x.begin(),x.end() 
#define SIZE(x) ll(x.size()) 

#define INF32 2147483647 //2.147483647×10^{9}:32bit整数のinf
#define INF64 9223372036854775807 //9.223372036854775807×10^{18}:64bit整数のinf
#define MOD 1000000007 //問題による

#define ll long long


#define F first
#define S second

#define coutALL(x) for(auto i=x.begin();i!=--x.end();i++)cout<<*i<<" ";cout<<*--x.end()<<endl;
#define coutALL2d(vv) for(const auto& v : vv){for(const auto& e : v){cout << e << " ";}cout << endl;}

#define vi vector<int>
#define vvi vector<vector<int> >
#define vll vector<long long>
#define vvll vector<vector<long long> >

vll v;
void f(ll n, ll s){
    if(n>s){
        v.push_back(s);
        return;
    }
    else{
        v.push_back(n);
        f(n-1,s-n);
        return;
    }

}

int main(){
    ll n,s;
    cin >> n >> s;

    if(n*(n+1)/2 < s){
        cout << -1 << endl;
    }
    else{
        f(n,s);
    }
    cout << v.size() << endl;
    rep(i,v.size()){
        cout << v[v.size()-1-i] << " ";
    }
    cout << endl;
}