Error Class 'Laracast\Flash\FlashServiceProvider' not found

I got error message while using Laracast flash package

 Error Output: PHP Fatal error:  Class 'Laracast\Flash\FlashServiceProvider'  
   not found in /var/www/demo/vendor/laravel/framework/src/Illuminate/Foundat  
  ion/ProviderRepository.php on line 146  

If any suggestion please let me know.

Thanks

via Chebli Mohamed