program project1 mode objfpc uses IFDEF UNIX IFDEF UseCThreads cthread

program project1;

{$mode objfpc}{$H+}

uses
  {$IFDEF UNIX}{$IFDEF UseCThreads}
  cthreads,
  {$ENDIF}{$ENDIF}
  Classes
  { you can add units after this };
 var t:text;
   a:array[1..6]of char;
   b,c,e,f,j:integer;

begin
  assign(t,'input.txt');
  reset(t);
  b:=1;
  a[6]:='k';
  while not eof(t) do begin
      read(t,a[b]);
      b:=b+1;
  end;
  if a[6] <> 'k' then begin
      j:=1;
  end;
  if a[1] = 'x' then begin
    e:=ord(a[3])-48;
    f:=ord(a[5])-48;
    if a[2] = '+' then begin
      c:=f - e;
    end;
    if a[2] = '-' then begin
       c:=f + e;
    end;
  end
  else begin
    e:=ord(a[1]) - 48;
    f:=ord(a[5]) - 48;
    if a[2] = '+' then begin
      c:=f - e;
    end;
    if a[2] = '-' then begin
       c:=f + e;
    end;
  end;
  close(t);
  assign(t,'output.txt');
  rewrite(t);
  if j = 1 then begin
    write(t,'not to be enter');
  end
  else begin
     write(t,c);
  end;
  close(t);
end.