diff --git a/app/models/contest.rb b/app/models/contest.rb
--- a/app/models/contest.rb
+++ b/app/models/contest.rb
@@ -1,2 +1,6 @@
 class Contest < ActiveRecord::Base
+
+  has_and_belongs_to_many :users
+  has_and_belongs_to_many :problems
+
 end