Retrieving User Avatar

hi stackideas team, i want retrieving the user avatar, but with that code
require_once(JPATH_ADMINISTRATOR . '/components/com_easysocial/includes/easysocial.php');
$id = 445;
$my = ES::user();
$avatar = $my->getAvatar($id);
but give me this error:

Notice: Use of undefined constant JPATH_ADMINISTRATOR - assumed 'JPATH_ADMINISTRATOR' in C:\xampp\htdocs\prefix\recuperaavatar.php on line 2

Warning: require_once(JPATH_ADMINISTRATOR/components/com_easysocial/includes/easysocial.php): failed to open stream: No such file or directory in C:\xampp\htdocs\prefix\recuperaavatar.php on line 2

Fatal error: require_once(): Failed opening required 'JPATH_ADMINISTRATOR/components/com_easysocial/includes/easysocial.php' (include_path='.;C:\xampp\php\PEAR') in C:\xampp\htdocs\prefix\recuperaavatar.php on line 2

can you help me please.