n, l = gets.split.map(&:to_i)
D = 998244353

def pow2mod(n)
  return 1 if 0 == n
  p = (pow2mod(n/2) ** 2)
  p *= 2 if 1 == n%2
  p % D
end

n = n - l + 1
puts (pow2mod(n) - 1) % D