Ownership changed from root to user :<

I've got some problems and to get them fixed, I changed the ownership on /usr from root to user. So many errors thrown afterward, while opening the VBs and basically could not login to root anymore! So the question is that how to get the ownership of /usr back to original, meaning from user's ownership to root ownership. Cause I run sudo -i and I get the operation is not permitted.

Have run the following command before the disaster!
chown -R USER /usr