( unroman
  =   nbr,lastVal,val
    .     0:?nbr:?lastVal
        & @( low$!arg
           :   ?
               %@?L
               ( ?
               &     (m.1000)
                     (d.500)
                     (c.100)
                     (l.50)
                     (x.10)
                     (v.5)
                     (i.1)
                 : ? (!L.?val) ?
               &     (!val:~>!lastVal|!val+-2*!lastVal)
                   + !nbr
                 : ?nbr
               & !val:?lastVal
               & ~
               )
           )
      | !nbr
  )
&     (M.1000)
      (MCXI.1111)
      (CMXI.911)
      (MCM.1900)
      (MCMXC.1990)
      (MMVIII.2008)
      (MMIX.2009)
      (MCDXLIV.1444)
      (MDCLXVI.1666)
      (MMXII.2012)
  : ?years
& (test=.out$(!arg unroman$!arg))
& (   !years
    : ? (?L.?D) (?&test$!L&~)
  | done
  );