How to add extra condition while login user form in laravel?

How to add extra condition in login form in laravel

 First open these folder

Yoursite|vendor\laravel\framework\src\Illuminate\Foundation\Auth

then find public function login(Request $request) this funcation

add these line at the top of funcation 

$user = User::where('email',$request->email)->first();
if($user && $user->role!=1){
      return redirect()->back()->with('error','You are not an admin.');
}

$user->role or any other condition which you want to check

then go to view where you will show this error

Copy and paste this code 

@if($message = Session::get('error'))
                        <div class="errorlv">
                            <i class="zmdi zmdi-alert-circle"></i> {{ $message }}
                        </div>
                        @endif