如何合并两个htaccess文件，第一个用于用户名，第二个用于隐藏php扩展

i want to merge this .htaccess file

RewriteEngine On
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule ^(.*)$ /profile.php?username=$1

with this

RewriteEngine On
RewriteCond %{REQUEST_FILENAME} !-f
RewriteRule ^([^\.]+)$ $1.php [NC]

they are both in the root directory

 RewriteEngine On
 RewriteCond %{REQUEST_FILENAME} !-f
 RewriteCond %{REQUEST_FILENAME} !-d
 RewriteRule ^(.*)$ /profile.php?username=$1
 RewriteRule ^([^\.]+)$ $1.php [NC]