Nginx rewrite rules for favicon.ico for multiple subdomains.

In nginx /etc/sites-avaliable/vhost_config_file, I have the following rewrite rules for serving multiple subdomains with their favicon.ico files:



if ($host = example1.example.com){
rewrite ^/favicon.ico$ /favicon_example.ico break;
}

if ($host = example2.example.com){
rewrite ^/favicon.ico$ /favicon_example.ico break;
}

if ($host = example3.example.com){
rewrite ^/favicon.ico$ /favicon_example.ico break;
}


Please, how can I make this simple operation by adding **ONE GENERAL REWRITE RULE**:

That rule must do:

1.For subdomains example1,example2... to check in location /images/$host.ico is there a favicon_example.ico file and serve it.

2.If there is no such file, than to serve just a plain favicon.ico file.

Thank's in advance...