git - Can't push to the heroku -

i pushing current git repository heroku. online application developed using scala , intellij. , don't know how fix error.

$ git push heroku master counting objects: 3, done. delta compression using 4 threads. compressing objects: 100% (3/3), done. writing objects: 100% (3/3), 531 bytes | 0 bytes/s, done. total 3 (delta 0), reused 0 (delta 0) remote: compressing source files... done. remote: building source: remote:  remote:  !     no default language detected app. remote:             hint: occurs when heroku cannot detect         buildpack use application automatically. remote:             see https://devcenter.heroku.com/articles/buildpacks remote:  remote:  !     push failed remote: verifying deploy.... remote:  remote: !   push rejected salty-coast-14102. remote:  https://git.heroku.com/salty-coast-14102.git  ! [remote rejected] master -> master (pre-receive hook declined) error: failed push refs 'https://git.heroku.com/salty-coast-14102.git' 

read doc explain do.
https://devcenter.heroku.com/articles/buildpacks

setting buildpack on application

you can change buildpack used application setting buildpack value.
when application next pushed, new buildpack used.

$ heroku buildpacks:set heroku/php 

buildpack set. next release on random-app-1234 use heroku/php.
run git push heroku master create new release using buildpack.

this whay not working since did not set up.

... when application next pushed, new buildpack used.

you may specify buildpack during app creation:

$ heroku create myapp --buildpack heroku/python