procedure befriend_con(s)
   local lseq, i, tail

   s := copy(s)

   lseq := [get(s)] | return []

   while i := get(s) do
      lseq |||:= connect(lseq[-1], i)

   return lseq

end

procedure connect(j, i)
   local k, result

   result := []

   k := i - j

   if abs(k) = 1 then put(result, i)
   else if k = 0 then
      put(result, i + ?[1, -1], i)
   else if k > 0 then
      every put(result, j + 1 to i)
   else
      every put(result, j - 1 to i by -1)

   return result

end