How can I make the build look like EXAMPLE1 from EXAMPLE2?EXAMPLE1:
index.php?showtopic=100&st=90
EXAMPLE2: index.php?s=ghhkgkhdfskjghdfk&showtopic=100&st=90

I have tried doing this, but no luck: 
%h%p/%n%[s:?s*&:?::].%t