n = read_line.chars.map(&.to_i)
cand = Array.new(n.size, 4)
if n < cand
  puts "5" * (n.size - 1)
  exit
end
cand.fill(5)
if cand <= n
  puts cand.join
  exit
end
lo = Array.new(n.size, 0)
hi = Array.new(n.size, 1)
mid = Array.new(n.size + 1, 0)
1000.times do |turn|
  carry = 0
  n.size.times do |i|
    carry += lo[i] + hi[i]
    mid[i] = carry % 2
    if i > 0
      cand[-i] = carry % 2 == 0 ? 4 : 5
    end
    carry //= 2
  end
  mid[n.size] = carry
  cand[0] = carry == 0 ? 4 : 5
  if cand <= n
    lo = mid[1..]
  else
    hi = mid[1..]
  end
end
puts lo.map { |v| v == 0 ? 4 : 5 }.reverse.join