#import std
#import nat

(# The input file contains one or more sudoku puzzles, each on one
line expressed as a sequence of 81 decimal digits in row major order,
with 0 as a place holder for the unassigned cells. #)

#executable (<'par'>,<>)
#optimize+

sudoku =

~command.files; <.file$[contents: --<''>]>+ *= ~contents.&F; * -+
   ~&rSL+ (psort (nleq+)* <~&blrl,~&blrr>)+ ~&arg^& -+
      ~&al?\~&ar ~&aa^&~&afahPRPfafatPJPRY+ ~&farlthlriNCSPDPDrlCS2DlrTS2J,
      ^|J/~& ~&rt!=+ ^= ~&s+ ~&H(
         -+.|=&lrr;,|=&lrl;,|=&ll;+-,
         ~&rgg&& ~&irtPFXlrjrXPS; ~&lrK2tkZ2g&& ~&llrSL2rDrlPrrPljXSPTSL)+-,
   //~&p ^|DlrDSLlrlPXrrPDSL(~&,num*+ rep2 block3)*= num block27 ~&iiK0 iota9,
   * `0?=\~&iNC ! ~&t digits+-