Use associative laws to show that [P ^(Q^R)]^S is equivalent to (P ^ Q) ^ (R ^ S).

I know you can switch anything inside the parentheses with anything outside so I got [R ^(Q^P)]^S but I don't know how to go about getting the S into the parentheses to make it look like (P ^ Q) ^ (R ^ S), or are you just allowed to do that because of the associative law?

Any help would be greatly appreciated.