php - .htaccess conflict between two rewrite rule

in my website two rewrite rule are conflicting with each other i have url for my users like= http://twekr.com/sam and all my website pages open like http://twekr.com/login

now here is htaccess file rules

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

RewriteRule ^([a-zA-Z0-9_-]+)$ profile.php?user=$1
RewriteRule ^([a-zA-Z0-9_-]+)/$ profile.php?user=$1
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Now only this rule works because its loaded first =

RewriteCond %{REQUEST_FILENAME} !-d
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And if i put profile rewrite rule above

RewriteRule ^([a-zA-Z0-9_-]+)$ profile.php?user=$1
RewriteRule ^([a-zA-Z0-9_-]+)/$ profile.php?user=$1 (then this works)
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and this doesnt

RewriteCond %{REQUEST_FILENAME} !-d (does not work)
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What is the problem in htaccess rule?