diff --git a/app/controllers/graders_controller.rb b/app/controllers/graders_controller.rb
--- a/app/controllers/graders_controller.rb
+++ b/app/controllers/graders_controller.rb
@@ -32,6 +32,7 @@
                            :order => 'created_at DESC')
     @last_test_request = TestRequest.find(:first,
                                           :order => 'created_at DESC')
+    @submission = Submission.order("id desc").limit(20)
   end
 
   def clear
diff --git a/app/controllers/main_controller.rb b/app/controllers/main_controller.rb
--- a/app/controllers/main_controller.rb
+++ b/app/controllers/main_controller.rb
@@ -63,7 +63,8 @@
     @submission.user = user
     @submission.language_id = 0
     if (params['file']) and (params['file']!='')
-      @submission.source = params['file'].read 
+      @submission.source = File.open(params['file'].path,'r:UTF-8',&:read) 
+      @submission.source.encode!('UTF-8','UTF-8',invalid: :replace, replace: '')
       @submission.source_filename = params['file'].original_filename
     end
     @submission.submitted_at = Time.new.gmtime
diff --git a/app/controllers/report_controller.rb b/app/controllers/report_controller.rb
--- a/app/controllers/report_controller.rb
+++ b/app/controllers/report_controller.rb
@@ -188,4 +188,29 @@
     user.each_value { |v| @summary[:solve] += 1 if v == 1 }
   end
 
+  def stuck #report struggling user,problem
+    # init
+    user,problem = nil
+    solve = true
+    tries = 0
+    @struggle = Array.new
+    record = {}
+    Submission.includes(:problem,:user).order(:problem_id,:user_id).find_each do |sub|
+      if user != sub.user_id or problem != sub.problem_id
+        @struggle << { user: record[:user], problem: record[:problem], tries: tries } unless solve
+        record = {user: sub.user, problem: sub.problem}
+        user,problem = sub.user_id, sub.problem_id
+        solve = false
+        tries = 0
+      end
+      if sub.points >= sub.problem.full_score
+        solve = true
+      else
+        tries += 1
+      end
+    end
+    @struggle.sort!{|a,b| b[:tries] <=> a[:tries] }
+    @struggle = @struggle[0..50]
+  end
+
 end
diff --git a/app/controllers/users_controller.rb b/app/controllers/users_controller.rb
--- a/app/controllers/users_controller.rb
+++ b/app/controllers/users_controller.rb
@@ -124,6 +124,7 @@
       @histogram[:data][d.to_i] += 1 if d < range
 
       @summary[:count] += 1
+      next unless sub.problem
       problem[sub.problem] = [problem[sub.problem], (sub.points >= sub.problem.full_score) ? 1 : 0].max
     end
 
diff --git a/app/views/graders/list.html.haml b/app/views/graders/list.html.haml
--- a/app/views/graders/list.html.haml
+++ b/app/views/graders/list.html.haml
@@ -24,28 +24,49 @@
       = submit_tag 'Clear all data'
   %br{:style => 'clear:both'}/
 
-- if @last_task
-  Last task:
-  = link_to "#{@last_task.id}", :action => 'view', :id => @last_task.id, :type => 'Task'
+%div{style: 'width:500px; float: left;'}
+  - if @last_task
+    Last task:
+    = link_to "#{@last_task.id}", :action => 'view', :id => @last_task.id, :type => 'Task'
+
+    %br/
+
+  - if @last_test_request
+    Last test_request:
+    = link_to "#{@last_test_request.id}", :action => 'view', :id => @last_test_request.id, :type => 'TestRequest'
+
+  %h2 Current graders
+
+  = render :partial => 'grader_list', :locals => {:grader_list => @grader_processes}
+
+  %h2 Stalled graders
+
+  = render :partial => 'grader_list', :locals => {:grader_list => @stalled_processes}
+
+  %h2 Terminated graders
 
-  %br/
+  = form_for :clear, :url => {:action => 'clear_terminated'} do |f|
+    = submit_tag 'Clear data for terminated graders'
 
-- if @last_test_request
-  Last test_request:
-  = link_to "#{@last_test_request.id}", :action => 'view', :id => @last_test_request.id, :type => 'TestRequest'
+  = render :partial => 'grader_list', :locals => {:grader_list => @terminated_processes}
+%div{}
+  %h2 Last 20 submissions
+  %table.graders
+    %thead
+      %th ID
+      %th User
+      %th Problem
+      %th Submitted
+      %th Graded
+      %th Result
+    %tbody
+      - @submission.each do |sub|
+        %tr.inactive
+          %td= link_to sub.id, controller: 'graders' ,action: 'submission', id: sub.id
+          %td= sub.try(:user).try(:full_name)
+          %td= sub.try(:problem).try(:full_name)
+          %td= "#{time_ago_in_words(sub.submitted_at)} ago"
+          %td= "#{time_ago_in_words(sub.graded_at)} ago"
+          %td= sub.grader_comment
 
 
-%h2 Current graders
-
-= render :partial => 'grader_list', :locals => {:grader_list => @grader_processes}
-
-%h2 Stalled graders
-
-= render :partial => 'grader_list', :locals => {:grader_list => @stalled_processes}
-
-%h2 Terminated graders
-
-= form_for :clear, :url => {:action => 'clear_terminated'} do |f|
-  = submit_tag 'Clear data for terminated graders'
-
-= render :partial => 'grader_list', :locals => {:grader_list => @terminated_processes}
diff --git a/app/views/report/_report_menu.html.haml b/app/views/report/_report_menu.html.haml
--- a/app/views/report/_report_menu.html.haml
+++ b/app/views/report/_report_menu.html.haml
@@ -3,5 +3,5 @@
   Reports
   %br/
   = link_to '[Hall of Fame]', :action => 'problem_hof'
-  = link_to '[Submission]', :action => 'submission_stat'
+  = link_to '[Struggle]', :action => 'stuck'
   = link_to '[Login]', :action => 'login_stat'
diff --git a/app/views/report/stuck.html.haml b/app/views/report/stuck.html.haml
new file mode 100644
--- /dev/null
+++ b/app/views/report/stuck.html.haml
@@ -0,0 +1,17 @@
+%table.info
+  %thead
+    %tr.info-head
+      %th Problem
+      %th User
+      %th tries
+  %tbody
+    - @struggle.each do |s|
+      %tr
+        %td
+          = link_to "(#{s[:problem].name})", controller: :problems, action: :stat, id: s[:problem]
+          = s[:problem].full_name
+        %td
+          = link_to "(#{s[:user].login})", controller: :users, action: :profile, id: s[:user]
+          = s[:user].full_name
+        %td
+          = s[:tries]