N, S = gets.split.map(&:to_i)

ans = [*1..N]
sum = N * (N + 1) / 2

while sum > S
  v = ans.pop
  sum -= v
end

if sum < S
  sum += ans.last + 1
  ans.push(ans.last + 1)
  diff = sum - S
  ans.delete_if { |a| a == diff }
end

puts ans.size
puts ans.join(' ')