text: def problem442():
      """
  
  
      An integer is called eleven-free if its decimal expansion does not contain
         any substring representing a power of 11 except 1.
  
         For example, 2404 and 13431 are eleven-free, while 911 and 4121331 are
         not.
  
         Let E(n) be the nth positive eleven-free integer. For example, E(3) = 3,
         E(200) = 213 and E(500 000) = 531563.
  
         Find E(10^18).
      """
  
      pass
  