typedef long long ll;
typedef long double ld;
#include <bits/stdc++.h>
using namespace std;
#define int long long
signed main(){
    ll n,s;
    std::cin >> n>>s;
    ll sum = n*(n+1)/2;
    vector<ll> ans;
    for (int i = n; i >= 1; i--) {
        if(sum-s>=i){
            sum -= i;
        }else{
            ans.push_back(i);
        }
    }
    sort(ans.begin(),ans.end());
    
    std::cout << ans.size() << std::endl;
    for (int i = 0; i < ans.size(); i++) {
        std::cout << ans[i];
        if(i<ans.size()-1){
            std::cout << " ";
        }
    }
    std::cout << std::endl;
}