program bbb (input,output, infile);

const
   blank = ' ';

var
   infile                                                       : text;
   c                                                            : char;
   eqn, equation                                                : string[20];
   digit1, digit2, digit3, digit4	                        : integer;
   previousnotblank, currentnotblank, legalinteger, previousnum : boolean;

{*****************}

procedure convert;

begin
   digit1:=ord(c)-ord('0');
end; { convert }


{****************}

procedure multidigits;

begin
   digit1:= digit1*10;

   digit3:= ord(c)-ord('0');

   digit1:= digit1+digit3;

   previousnum:=legalinteger;

end; { multidigits }

{****************}

procedure multidigits2;

begin
   digit2:= digit2*10;

   digit4:= ord(c)-ord('0');

   digit2:= digit2+digit4;

   previousnum:=legalinteger;

end; { multidigits }

{*****************}

procedure convert2 ;

begin
   legalinteger:= (ord(c)<=ord('9')) and (ord(c)>=ord('0'));

   if c='-' then
   begin
      read(infile,c);

      if (ord(c)<=ord('9')) and (ord(c)>=ord('0')) then
      begin
         digit2:=ord('0')-ord(c);
         previousnum:=legalinteger;
      end;
   end;

  while legalinteger and (c<>'+') do
   begin

      if legalinteger and previousnum then
         multidigits2
      else

         if legalinteger then
           begin
         
            digit2:=ord(c)-ord('0');
            writeln('convert2: digit2= ',digit2);
            previousnum:=legalinteger;
         
           end;

      if not eoln(infile) then
         read(infile,c)
      else
         legalinteger:=false;

   end;

      if (ord(c)>ord('9')) or (ord(c)<ord('0')) then
        begin
          writeln('error');

          if (c=' ') then
             writeln("There can't be an operation sign at the end.");
             equation:='notcorrect';
        end;


end; { convert2 }


{****************}

procedure plus;
begin

   read(infile,c);

   currentnotblank:= c <> blank;

   previousnum:=false;

   if not currentnotblank then
        begin
           while (c = blank) and not eoln(infile) do
              begin
              read(infile,c);
              end;
           convert2;
           digit1:=digit1+digit2;

        end;

   if currentnotblank then
      begin
         convert2;
         digit1:= digit1+digit2;
      end;

end; { plus }

{****************}
begin
   assign(infile, 'input.txt');

   writeln('Enter equation: ');
   readln(eqn);

   rewrite(infile);
   write(infile,eqn);
   writeln(infile);

   reset(infile);

   while not eof(infile) do
      begin
         previousnum:=false;

   while not eoln(infile) do
   begin

      read(infile,c);
      currentnotblank:= c<>blank;

      if currentnotblank then
      begin

         if (ord(c)>ord('9')) or (ord(c)<ord('*')) or (c='.') or (c='\') then
            begin
               writeln(' There is an error within the equation ');
               equation:= 'notcorrect';
            end;

         legalinteger:= (ord(c)<=ord('9')) and (ord(c)>=ord('0'));

         if legalinteger and previousnum then
            multidigits
         else
         if legalinteger then
            begin
               convert;
               previousnum:=legalinteger;
            end;

         if (c='+') then
            plus
      else
         if (c='*') then
            multi
      else
         if (c='/') then
            divide
      else
         if (c='-') then
            subtract;

      end;


   end; {while not eoln}

   if equation = 'notcorrect' then
      write('There is no answer.')
   else
      write('The answer is: ',digit1);

    writeln;
    readln(infile);

   end; {while not eof}

end.