local n, s = io.read("*n", "*n")
local t = {}
for i = n, 1, -1 do
  if i <= s then
    table.insert(t, i)
    s = s - i
  end
end
for i = 1, #t do
  local j = #t + 1 - i
  if j <= i then break end
  t[i], t[j] = t[j], t[i]
end
print(#t)
print(table.concat(t, " "))