RewriteEngine On
RewriteBase /

RewriteRule ^c3031/([^/]+)/((30|31)|confirm|cancel)/?$ /r_30_31.php?k=$1&a=$2 [L,QSA,NC]
RewriteRule ^c/([^/]+)/([01]|confirm|cancel)/?$ /r.php?k=$1&a=$2 [L,QSA,NC]