//queens_it.cpp --> *.pas
var
  arow, aleft, aright, aposs : array[0..31] of integer;
  N, count, poss, place, val, pos : integer;    
begin
  N:=1;
  repeat
  write('N=',N:2);
  count := 0;    
  val := (1 shl N) -1;
  pos := 1;
  arow[1] := 0;
  aleft[1] := 0;
  aright[1] := 0;
  aposs[1] := val shr (N div 2);
  poss := aposs[1];
  while(pos <> 0) do begin
    if(poss <>0) then begin
      place := poss and -poss;
      poss := poss and not place;
      if (pos = 1) and (poss = 0) and ((N and 1) <> 0) then
        count := count shl 1;
      if (pos <> N) then begin
        arow[pos + 1] := arow[pos] or place;
        aleft[pos + 1] := (aleft[pos] or place) shl 1;  
        aright[pos + 1] := (aright[pos] or place) shr 1;    
        aposs[pos] := poss;
        pos := pos + 1;                
        poss := not(arow[pos] or aleft[pos] or aright[pos]) and val;
        aposs[pos] := poss;
      end else count := count + 1;
    end else begin
      pos := pos - 1; poss := aposs[pos];
    end;
  end;
  if( not( (N and 1) <> 0) ) then count := count shl 1;
  writeln(' count=', count : 1);
  N:=N+1;
  until N=0;
end.