Factorial in Apache rewrite rules

factorial.htaccess

Options +FollowSymLinks

RewriteEngine On
RewriteBase /

RewriteRule ^just/(1*)/?$ /index.php?just=$1 [L]

RewriteRule ^add-and/(\w+)/1(1*)/(1+)(/.*)$ /$1/$2$3$4

RewriteRule ^add/(1+)/(1+)/?$ /add-and/just/$1/$2/

RewriteRule ^mul-and/(\w+)/(1+)/(1+)(/.*)$ /mul-and-b/$1/1/$2/$3$4
RewriteRule ^mul-and-b/(\w+)/(1+)/1/(1+)(/.*)$ /$1/$2$4
RewriteRule ^mul-and-b/(\w+)/(1+)/1(1+)/1(1*)(/.*)$ /mul-and-b/$1/$2$4/$3/1$4$5

RewriteRule ^mul/(1+)/(1+)/?$ /mul-and/just/$1/$2/

RewriteRule ^fac/(1+)/?$ /fac_b/11/$1
RewriteRule ^fac_b/(1+)/1/?$ /just/$1
RewriteRule ^fac_b/(1+)/1(1+)/?$ /mul-and/fac_b/$1/1$2/$2