var dung:boolean;
    i,kt:integer;
    s:string;
begin
     writeln('Nhap xau co cac dau ( va ): '); readln(s);
     dung:=true;
     kt:=0;
     for i:=1 to length(s) do
     begin
          if s[i]='(' then inc(kt)
          else if s[i]=')' then dec(kt);
          if kt<0 then 
          begin
               dung:=false;
               exit;
          end;
     end;
     if (dung=true) and (kt=0) then write('Ngoac dung')
     else write('Ngoac khong dung');
     readln;
end.