How can update Exchange 2013 from RTM to CU23 ?

Dear all,

Now, my exchange 2013 is version RTM (first), I want update to version CU 23.

Can I update directly from version RTM to version CU23 ? or have to update via the intermediate version. Currently, MS does not allow downloads of versions older than version 21. Please help me update the version.

Thanks you so much.