I am able to deploy my basic sinatra app on heroku but running it gives "APP CRASHES" error

running "heroku logs" give the following error. I am using ruby1.9.1. dont know why this ruby1.8.7 shows in the backtrace. Please help

anmol@anmol-laptop:heroku$ heroku logs /usr/ruby1.8.7/lib/ruby/site_ruby/1.8/rubygems/custom_require.rb:31:in gem_original_require': no such file to load -- sinatra (LoadError) from /usr/ruby1.8.7/lib/ruby/site_ruby/1.8/rubygems/custom_require.rb:31:inrequire' from ./main.rb:2 from /usr/ruby1.8.7/lib/ruby/site_ruby/1.8/rubygems/custom_require.rb:31:in gem_original_require' from /usr/ruby1.8.7/lib/ruby/site_ruby/1.8/rubygems/custom_require.rb:31:inrequire' from config.ru:1 from /home/heroku_rack/heroku.ru:23 from /usr/ruby1.8.7/lib/ruby/gems/1.8/gems/rack-1.0.1/lib/rack/builder.rb:29:in instance_eval' from /usr/ruby1.8.7/lib/ruby/gems/1.8/gems/rack-1.0.1/lib/rack/builder.rb:29:ininitialize' from /usr/ruby1.8.7/lib/ruby/gems/1.8/gems/rack-1.0.1/lib/rack/builder.rb:46:in new' from /usr/ruby1.8.7/lib/ruby/gems/1.8/gems/rack-1.0.1/lib/rack/builder.rb:46:inmap' from /home/heroku_rack/heroku.ru:18 from /usr/ruby1.8.7/lib/ruby/gems/1.8/gems/rack-1.0.1/lib/rack/builder.rb:29:in instance_eval' from /usr/ruby1.8.7/lib/ruby/gems/1.8/gems/rack-1.0.1/lib/rack/builder.rb:29:ininitialize' from /home/heroku_rack/heroku.ru:11:in new' from /home/heroku_rack/heroku.ru:11 from /usr/ruby1.8.7/lib/ruby/gems/1.8/gems/rack-1.0.1/lib/rack/builder.rb:29:ininstance_eval' from /usr/ruby1.8.7/lib/ruby/gems/1.8/gems/rack-1.0.1/lib/rack/builder.rb:29:in initialize' from /home/heroku_rack/heroku.ru:1:innew' from /home/heroku_rack/heroku.ru:1

==> dyno-3277552.log (crash) <== /usr/ruby1.8.7/lib/ruby/site_ruby/1.8/rubygems/custom_require.rb:31:in gem_original_require': no such file to load -- sinatra (LoadError) from /usr/ruby1.8.7/lib/ruby/site_ruby/1.8/rubygems/custom_require.rb:31:inrequire' from ./main.rb:2 from /usr/ruby1.8.7/lib/ruby/site_ruby/1.8/rubygems/custom_require.rb:31:in gem_original_require' from /usr/ruby1.8.7/lib/ruby/site_ruby/1.8/rubygems/custom_require.rb:31:inrequire' from config.ru:1 from /home/heroku_rack/heroku.ru:23 from /usr/ruby1.8.7/lib/ruby/gems/1.8/gems/rack-1.0.1/lib/rack/builder.rb:29:in instance_eval' from /usr/ruby1.8.7/lib/ruby/gems/1.8/gems/rack-1.0.1/lib/rack/builder.rb:29:ininitialize' from /usr/ruby1.8.7/lib/ruby/gems/1.8/gems/rack-1.0.1/lib/rack/builder.rb:46:in new' from /usr/ruby1.8.7/lib/ruby/gems/1.8/gems/rack-1.0.1/lib/rack/builder.rb:46:inmap' from /home/heroku_rack/heroku.ru:18 from /usr/ruby1.8.7/lib/ruby/gems/1.8/gems/rack-1.0.1/lib/rack/builder.rb:29:in instance_eval' from /usr/ruby1.8.7/lib/ruby/gems/1.8/gems/rack-1.0.1/lib/rack/builder.rb:29:ininitialize' from /home/heroku_rack/her开发者_JAVA百科oku.ru:11:in new' from /home/heroku_rack/heroku.ru:11 from /usr/ruby1.8.7/lib/ruby/gems/1.8/gems/rack-1.0.1/lib/rack/builder.rb:29:ininstance_eval' from /usr/ruby1.8.7/lib/ruby/gems/1.8/gems/rack-1.0.1/lib/rack/builder.rb:29:in initialize' from /home/heroku_rack/heroku.ru:1:innew' from /home/heroku_rack/heroku.ru:1

-----> Your application is requiring a file that it can't find.

   Most often this is due to missing gems, or it could be that you failed
   to commit the file to your repo.  See http://docs.heroku.com/gems for
   more information on managing gems.

Examine the backtrace above this message to debug.

create a file with a name ".gems" and include this line "sinatra".

by this way you are instructing to include sinatra gem

More information is here: http://docs.heroku.com/rack#sinatra