implementation
 const
     alph36 = '0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ';
function CharToLongNumber(val: char; base: TBase): TLongNumber;
var num: int64;
begin
	num := Pos(val, alph36);
  if (num > 0) and (num-1 < base)  then begin
  	Result := num-1;
	end
  else
  raise Exception.Create('Invalid char ''' + val + '''');

end;
function Invers(Res: TLongNumber): TLongNumber;
var
   arr: TLongNumber;
   i: integer;
begin
      SetLength(arr.dig, high(res.dig)+1);
      for i := 0 to high(res.dig) do begin
          arr.dig[high(arr.dig)-i] := res.dig[i];
      end;
      arr.inv := res.inv;
      Result := arr;
end;
function fromString(const str: AnsiString; base: TBase): TLongNumber;
var i, n: integer;
   res, c: TLongNumber;
begin
  res := 0;
  if str = '' then exit(res);
  if (str = '0') or (str = '-0') then res.inv := true;
  if (str[1] = '-') then begin
     res.inv := false;
     n := 2;
  end
  else begin
       res.inv := true;
       n :=  1;
  end;
  while((str[n] = '0') and (n < Length(str))) do n+=1;

  for i:=n to length(str) do begin
      c := charToLongNumber(str[i], base);
      Res := Res * base + c;
  end;
  if (str[1] = '-') then begin
     res.inv := false;

end;
  exit(res);

end;
function toString(const val: TLongNumber; base: TBase): AnsiString;
var res, buf: TLongNumber;
   c: longWord;
begin
  Result := '';
  res := val;
  buf := base;

  while (CompareModule(res,buf)) do begin
  	res := divmod(res, base, c);
    Result += alph36[c+1];
  end;
  res := divmod(res, base, c);
  Result += IntToStr(c);
  if (res.inv = false) then begin
  	Result += '-';
  end;
  Result := invers_str(result);
end;