Git push error 해결방법

$ git push origin master To https://github.com/mrkyel/SSR.git ! [rejected] master -> master (non-fast-forward) error: failed to push some refs to (url) hint: Updates were rejected because the tip of your current branch is behind hint: its remote counterpart. Integrate the remote changes (e.g. hint: 'git pull ...') before pushing again. hint: See the 'Note about fast-forwards' in 'git push --help..