protected function validator(Request $request)
    {
        return Validator::make($request, [
            'title' => 'required|max:255',
            'content' => 'required|max:500',
            'category' => 'required|max:3',
            'sum' => 'required|max:10',
            'city' => 'required|max:255',
                 ]);
        if ($validator->fails()) {
            return redirect('post/create')
                        ->withErrors($validator)
                        ->withInput();
                }
    }