\setupitemgroup
  [itemize]
  [broad,joinedup,packed,autointro]

\starttext

    \setupitemize[itemalign=flushright]

    \startitemize[n,repeat]
        \startitem level a
            \startitemize[n,norepeat]
                \startitem level b
                    \startitemize[A]
                        \startitem
                            level c
                        \stopitem
                    \stopitemize
                \stopitem
            \stopitemize
        \stopitem
    \stopitemize

\stoptext
