/* -*- coding: utf-8 -*-
 *
 * 2027.cc:  No.2027 (1, 2, 3, …, N) 's Subset Sum - yukicoder
 */

#include<cstdio>
#include<algorithm>
 
using namespace std;

/* constant */

const int MAX_N = 200000;

/* typedef */

typedef long long ll;

/* global variables */

int as[MAX_N];

/* subroutines */

/* main */

int main() {
  int n;
  ll s;
  scanf("%d%lld", &n, &s);

  int k = 0;
  for (int a = n; a >= 1; a--)
    if (s >= a) as[k++] = a, s -= a;

  printf("%d\n", k);
  for (int i = k - 1; i >= 0; i--)
    printf("%d%c", as[i], (i > 0) ? ' ' : '\n');
  
  return 0;
}