How to restrict Folder creation in MOSS 2007 for Document library?

Dear All,

We are working on MOSS 2007 document library. we have created Custom Folder Content types. users are having Contribute permission. They should not allow to create folders, but they can upload documents.

I tried with the custom level permission. but if I remove Add Items for List. they cannot able upload the files also.

How this can be possible?

Thanks & Regards,
Krishna.