#include <bits/stdc++.h> #include <atcoder/all> using namespace std; using namespace atcoder; #define rep(i,n) for(int i = 0; i < (int)(n); ++i) #define rrep(i,n) for(int i = (int)(n) - 1; i >= 0; --i) #define ALL(a) a.begin(), a.end() #define Sort(a) sort(a.begin(), a.end()) #define RSort(a) sort(a.rbegin(), a.rend()) typedef long long int ll; typedef long double ld; typedef vector<int> vi; typedef vector<long long> vll; typedef vector<char> vc; typedef vector<string> vst; typedef vector<double> vd; typedef pair<long long, long long> P; const long long INF = 0x1fffffffffffffff; const long long MOD = 1000000007; const long double PI = acos(-1); template<class T> inline bool chmax(T& a, T b) { if (a < b) { a = b; return 1; } return 0; } template<class T> inline bool chmin(T& a, T b) { if (a > b) { a = b; return 1; } return 0; } template<class T, class U> inline T vin(T& vec, U n) { vec.resize(n); for(int i = 0; i < (int) n; ++i) cin >> vec[i]; return vec; } template<class T> inline void vout(T vec, string s = "\n"){ for(auto x : vec) cout << x << s; } template<class... T> void in(T&... a){ (cin >> ... >> a); } void out(){ cout << '\n'; } template<class T, class... Ts> void out(const T& a, const Ts&... b){ cout << a; (cout << ... << (cout << ' ', b)); cout << '\n'; } template<class T, class U> void inGraph(vector<vector<T>>& G, U n, U m, bool directed = false){ G.resize(n); for(int i = 0; i < m; i++){ int a, b; cin >> a >> b; a--, b--; G[a].push_back(b); if(!directed) G[b].push_back(a); } } int main(){ ll n, s; in(n, s); vll ans; for(int i = n; i >= 1; i--){ ll sub = s - i; if(sub < 0) continue; ans.push_back(i); s -= i; } if(s != 0){ out(-1); return 0; } reverse(ALL(ans)); out((int) ans.size()); vout(ans, " "); }