def comp(n1, n2)
  return 1  if n1 == 4 && n2 == 7
  return -1 if n1 == 7 && n2 == 4

  n1 <=> n2
end

def main(a, b)
  ca = a.to_s.chars
  cb = b.to_s.chars

  return b if ca.size < cb.size
  return a if ca.size > cb.size

  [ca, cb].transpose.each do |_a, _b|
    case comp(_a.to_i, _b.to_i)
    when 1 then return a
    when -1 then return b
    end
  end
end


if __FILE__ == $0
  p main(*gets.split(" ").map(&:to_i))
end