diff --git a/app/controllers/problems_controller.rb b/app/controllers/problems_controller.rb
--- a/app/controllers/problems_controller.rb
+++ b/app/controllers/problems_controller.rb
@@ -150,11 +150,26 @@
 
   def stat
     @problem = Problem.find(params[:id])
-    if !@problem.available
+    unless @problem.available or session[:admin]
       redirect_to :controller => 'main', :action => 'list'
-    else
-      @submissions = Submission.includes(:user).where(problem_id: params[:id]).order(:user_id,:id)
+      return
     end
+    @submissions = Submission.includes(:user).where(problem_id: params[:id]).order(:user_id,:id)
+
+    #stat summary
+    range =65
+    @histogram = { data: Array.new(range,0), summary: {} }
+    @histogram[:data] = Array.new(range,0)
+    user = Hash.new(0)
+    @submissions.find_each do |sub|
+      d = (DateTime.now.in_time_zone - sub.submitted_at) / 24 / 60 / 60
+      @histogram[:data][d.to_i] += 1 if d < range
+      user[sub.user_id] = [user[sub.user_id], (sub.points >= @problem.full_score) ? 1 : 0].max
+    end
+    @histogram[:summary][:max] = [@histogram[:data].max,1].max
+
+    @summary = { attempt: user.count, solve: 0 }
+    user.each_value { |v| @summary[:solve] += 1 if v == 1 }
   end
 
   def manage
@@ -257,4 +272,7 @@
     problems
   end
 
+  def get_problems_stat
+  end
+
 end
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
@@ -105,91 +105,88 @@
       end
     end
 
-    if @problem
-      #aggregrate by language
-      @by_lang = {}
-      Submission.where(problem_id: @problem.id).find_each do |sub|
-        lang = Language.find_by_id(sub.language_id)
-        next unless lang
-        next unless sub.points >= @problem.full_score
+    return unless @problem
+
+    @by_lang = {} #aggregrate by language
 
-        #initialize
-        unless @by_lang.has_key?(lang.pretty_name)
-          @by_lang[lang.pretty_name] = {
-            runtime: { avail: false, value: 2**30-1 },
-            memory: { avail: false, value: 2**30-1 },
-            length: { avail: false, value: 2**30-1 },
-            first: { avail: false, value: DateTime.new(3000,1,1) }
-          }
-        end
+    range =65
+    @histogram = { data: Array.new(range,0), summary: {} }
+    @histogram[:data] = Array.new(range,0)
+    @summary = {count: 0, solve: 0, attempt: 0}
+    user = Hash.new(0)
+    Submission.where(problem_id: @problem.id).find_each do |sub|
+      #histogram
+      d = (DateTime.now.in_time_zone - sub.submitted_at) / 24 / 60 / 60
+      @histogram[:data][d.to_i] += 1 if d < range
 
-        if sub.max_runtime and sub.max_runtime < @by_lang[lang.pretty_name][:runtime][:value]
-          @by_lang[lang.pretty_name][:runtime] = {
-            avail: true,
-            user_id: sub.user_id,
-            value: sub.max_runtime,
-            sub_id: sub.id
-          }
-        end
+      @summary[:count] += 1
+      user[sub.user_id] = [user[sub.user_id], (sub.points >= @problem.full_score) ? 1 : 0].max
 
-        if sub.peak_memory and sub.peak_memory < @by_lang[lang.pretty_name][:memory][:value]
-          @by_lang[lang.pretty_name][:memory] = {
-            avail: true,
-            user_id: sub.user_id,
-            value: sub.peak_memory,
-            sub_id: sub.id
-          }
-        end
+      lang = Language.find_by_id(sub.language_id)
+      next unless lang
+      next unless sub.points >= @problem.full_score
 
-        if sub.submitted_at and sub.submitted_at < @by_lang[lang.pretty_name][:first][:value] and
-           !sub.user.admin?
-          @by_lang[lang.pretty_name][:first] = {
-            avail: true,
-            user_id: sub.user_id,
-            value: sub.submitted_at,
-            sub_id: sub.id
-          }
-        end
+      #initialize
+      unless @by_lang.has_key?(lang.pretty_name)
+        @by_lang[lang.pretty_name] = {
+          runtime: { avail: false, value: 2**30-1 },
+          memory: { avail: false, value: 2**30-1 },
+          length: { avail: false, value: 2**30-1 },
+          first: { avail: false, value: DateTime.new(3000,1,1) }
+        }
+      end
 
-        if @by_lang[lang.pretty_name][:length][:value] > sub.effective_code_length
-          @by_lang[lang.pretty_name][:length] = {
-            avail: true,
-            user_id: sub.user_id,
-            value: sub.effective_code_length,
-            sub_id: sub.id
-          }
-        end
-      end
-      
-      #process user_id
-      @by_lang.each do |lang,prop|
-        prop.each do |k,v|
-          v[:user] = User.exists?(v[:user_id]) ? User.find(v[:user_id]).full_name : "(NULL)"
-        end
+      if sub.max_runtime and sub.max_runtime < @by_lang[lang.pretty_name][:runtime][:value]
+        @by_lang[lang.pretty_name][:runtime] = { avail: true, user_id: sub.user_id, value: sub.max_runtime, sub_id: sub.id }
       end
 
-      #sum into best
-      if @by_lang and @by_lang.first
-        @best = @by_lang.first[1].clone
-        @by_lang.each do |lang,prop|
-          if @best[:runtime][:value] >= prop[:runtime][:value]
-            @best[:runtime] = prop[:runtime]
-            @best[:runtime][:lang] = lang
-          end
-          if @best[:memory][:value] >= prop[:memory][:value]
-            @best[:memory] = prop[:memory]
-            @best[:memory][:lang] = lang
-          end
-          if @best[:length][:value] >= prop[:length][:value]
-            @best[:length] = prop[:length]
-            @best[:length][:lang] = lang
-          end
-          if @best[:first][:value] >= prop[:first][:value]
-            @best[:first] = prop[:first]
-            @best[:first][:lang] = lang
-          end
+      if sub.peak_memory and sub.peak_memory < @by_lang[lang.pretty_name][:memory][:value]
+        @by_lang[lang.pretty_name][:memory] = { avail: true, user_id: sub.user_id, value: sub.peak_memory, sub_id: sub.id }
+      end
+
+      if sub.submitted_at and sub.submitted_at < @by_lang[lang.pretty_name][:first][:value] and
+          !sub.user.admin?
+        @by_lang[lang.pretty_name][:first] = { avail: true, user_id: sub.user_id, value: sub.submitted_at, sub_id: sub.id }
+      end
+
+      if @by_lang[lang.pretty_name][:length][:value] > sub.effective_code_length
+        @by_lang[lang.pretty_name][:length] = { avail: true, user_id: sub.user_id, value: sub.effective_code_length, sub_id: sub.id }
+      end
+    end
+
+    #process user_id
+    @by_lang.each do |lang,prop|
+      prop.each do |k,v|
+        v[:user] = User.exists?(v[:user_id]) ? User.find(v[:user_id]).full_name : "(NULL)"
+      end
+    end
+
+    #sum into best
+    if @by_lang and @by_lang.first
+      @best = @by_lang.first[1].clone
+      @by_lang.each do |lang,prop|
+        if @best[:runtime][:value] >= prop[:runtime][:value]
+          @best[:runtime] = prop[:runtime]
+          @best[:runtime][:lang] = lang
+        end
+        if @best[:memory][:value] >= prop[:memory][:value]
+          @best[:memory] = prop[:memory]
+          @best[:memory][:lang] = lang
+        end
+        if @best[:length][:value] >= prop[:length][:value]
+          @best[:length] = prop[:length]
+          @best[:length][:lang] = lang
+        end
+        if @best[:first][:value] >= prop[:first][:value]
+          @best[:first] = prop[:first]
+          @best[:first][:lang] = lang
         end
       end
     end
+
+    @histogram[:summary][:max] = [@histogram[:data].max,1].max
+    @summary[:attempt] = user.count
+    user.each_value { |v| @summary[:solve] += 1 if v == 1 }
   end
+
 end
diff --git a/app/models/problem.rb b/app/models/problem.rb
--- a/app/models/problem.rb
+++ b/app/models/problem.rb
@@ -54,6 +54,13 @@
   def self.download_file_basedir
     return "#{Rails.root}/data/tasks"
   end
+
+  def get_submission_stat
+    result = Hash.new
+    #total number of submission
+    result[:total_sub] = Submission.where(problem_id: self.id).count
+    result[:attempted_user] = Submission.where(problem_id: self.id).group_by(:user_id)
+  end
   
   protected
 
diff --git a/app/views/application/_bar_graph.html.haml b/app/views/application/_bar_graph.html.haml
new file mode 100644
--- /dev/null
+++ b/app/views/application/_bar_graph.html.haml
@@ -0,0 +1,44 @@
+- param = {} unless param
+- graph_height = param[:graph_height] || 100
+- bar_width = param[:bar_width] || 14
+- graph_width = (bar_width * histogram[:data].count) + 20
+:css
+  .hist_bar {
+    width: #{bar_width-1}px;
+    position: absolute;
+    background-color: lightblue;
+  }
+  .hist_fill {
+    width: #{bar_width-1}px;
+    position: absolute;
+    background-color: #eee;
+  }
+  .hist_text {
+    position: absolute;
+    font-size:5px;
+  }
+
+%div{style: "position: relative; width: #{graph_width}px; height: 150px; background-color:#fff;" }
+  //draw background
+  - histogram[:data].each_index do |i|
+    - height = histogram[:data][i] * graph_height / histogram[:summary][:max]
+    - top = graph_height - height
+    - left = graph_width - (i+1)*bar_width
+    %div.hist_fill{style: "top: 0px; height: #{graph_height - height}px; left: #{left}px;" }
+  // draw horizontal line
+  - line = 3
+  - line.times do |i|
+    - top = graph_height - graph_height * (i+0.5)/ line
+    %div{style: "position:absolute;width: #{graph_width-21}px;height: 1px;left: 20px;top:#{top}px;background-color: #333;"}
+    %div.hist_text{style: "position:absolute;left: 0px;top:#{top-6}px"}
+      =((i+0.5) * histogram[:summary][:max] / line).to_i
+  // draw the actual bar and text
+  - @histogram[:data].each_index do |i|
+    - height = histogram[:data][i] * graph_height / histogram[:summary][:max]
+    - top = graph_height - height
+    - left = graph_width - (i+1)*bar_width
+    %div.hist_bar{style: "top: #{top}px; height: #{height}px; left: #{left}px; dae: #{histogram[:data][i]}" }
+    - if i % 7 == 1
+      %div.hist_text{style: "top:#{graph_height + 5}px;left: #{left}px;"} #{(Time.zone.today - i.day).strftime('%-d')}
+    - if (Time.now.in_time_zone - i.day).day == 15
+      %div.hist_text{style: "top:#{graph_height + 15}px;left: #{left}px;"} #{(Time.zone.today - i.day).strftime('%b')}
diff --git a/app/views/problems/stat.html.haml b/app/views/problems/stat.html.haml
--- a/app/views/problems/stat.html.haml
+++ b/app/views/problems/stat.html.haml
@@ -6,6 +6,23 @@
 %h1 Problem stat: #{@problem.name}
 %h2 Overview
 
+
+%table.info
+  %thead
+    %tr.info-head
+      %th Stat
+      %th Value
+  %tbody
+    %tr{class: cycle('info-even','info-odd')}
+      %td Submissions
+      %td= @submissions.count
+    %tr{class: cycle('info-even','info-odd')}
+      %td Solved/Attempted User
+      %td #{@summary[:solve]}/#{@summary[:attempt]} (#{(@summary[:solve]*100.0/@summary[:attempt]).round(1)}%)
+
+%h2 Submissions Count
+= render partial: 'application/bar_graph', locals: { histogram: @histogram }
+
 %h2 Submissions
 - if @submissions and @submissions.count > 0
   %table.info#main_table
diff --git a/app/views/report/_task_hof.html.haml b/app/views/report/_task_hof.html.haml
--- a/app/views/report/_task_hof.html.haml
+++ b/app/views/report/_task_hof.html.haml
@@ -2,47 +2,66 @@
   .hof_user { color: orangered; font-style: italic; }
   .hof_language { color: green; font-style: italic; }
   .hof_value { color: deeppink;font-style: italic; }
+  .info_param { font-weight: bold;text-align: right; }
 
-%h2 Overall of #{Problem.find(params[:id]).full_name}
+%h1 (#{Problem.find(params[:id]).name}) #{Problem.find(params[:id]).full_name}
+
+%h2 Problem Stat
+%table.info
+  %thead
+    %tr.info-head
+      %th Stat
+      %th Value
+  %tbody
+    %tr{class: cycle('info-even','info-odd')}
+      %td.info_param Submissions
+      %td= @summary[:count]
+    %tr{class: cycle('info-even','info-odd')}
+      %td.info_param Solved/Attempted User
+      %td #{@summary[:solve]}/#{@summary[:attempt]} (#{(@summary[:solve]*100.0/@summary[:attempt]).round(1)}%)
+    - if @best
+      %tr{class: cycle('info-even','info-odd')}
+        %td.info_param Best Runtime
+        %td
+          by #{link_to @best[:runtime][:user], controller:'users', action:'profile', id:@best[:memory][:user_id]} 
+          using <span class="hof_language">#{@best[:runtime][:lang]}</span> 
+          with <span class="hof_value">#{@best[:runtime][:value] * 1000} milliseconds</span> 
+          at submission
+          = link_to("#" + @best[:runtime][:sub_id].to_s, controller: 'graders', action: 'submission', id:@best[:runtime][:sub_id])
+
+      %tr{class: cycle('info-even','info-odd')}
+        %td.info_param Best Memory Usage
+        %td
+          by #{link_to @best[:memory][:user], controller:'users', action:'profile', id:@best[:memory][:user_id]} 
+          using <span class="hof_language">#{@best[:memory][:lang]}</span> 
+          with <span class="hof_value">#{number_with_delimiter(@best[:memory][:value])} kbytes </span> 
+          at submission
+          = link_to("#" + @best[:memory][:sub_id].to_s, controller: 'graders' , action: 'submission', id:@best[:memory][:sub_id])
+
+      %tr{class: cycle('info-even','info-odd')}
+        %td.info_param Shortest Code
+        %td
+          by #{link_to @best[:length][:user], controller:'users', action:'profile', id:@best[:length][:user_id]} 
+          using <span class="hof_language">#{@best[:length][:lang]}</span> 
+          with  <span class="hof_value">#{@best[:length][:value]} bytes</span> 
+          at submission
+          = link_to("#" + @best[:length][:sub_id].to_s, controller: 'graders' , action: 'submission', id: @best[:length][:sub_id])
+
+      %tr{class: cycle('info-even','info-odd')}
+        %td.info_param First solver
+        %td
+          #{link_to @best[:first][:user], controller:'users', action:'profile', id:@best[:first][:user_id]} is the first solver 
+          using <span class="hof_language">#{@best[:first][:lang]}</span> 
+          on <span class="hof_value">#{@best[:first][:value]}</span> 
+          at submission
+          = link_to("#" + @best[:first][:sub_id].to_s, controller: 'graders' , action: 'submission', id: @best[:first][:sub_id])
+
+
+%p
+  This counts only for submission with 100% score <br/>
+  Right now, java is excluded from memory usage competition. (Because it always uses 2GB memory...)
 
 - if @best
-  %b Best Runtime:
-  by #{link_to @best[:runtime][:user], controller:'users', action:'profile', id:@best[:memory][:user_id]} 
-  using <span class="hof_language">#{@best[:runtime][:lang]}</span> 
-  with <span class="hof_value">#{@best[:runtime][:value] * 1000} milliseconds</span> 
-  at submission
-  = link_to("#" + @best[:runtime][:sub_id].to_s, controller: 'graders', action: 'submission', id:@best[:runtime][:sub_id])
-  %br/
-
-  %b Best Memory Usage:
-  by #{link_to @best[:memory][:user], controller:'users', action:'profile', id:@best[:memory][:user_id]} 
-  using <span class="hof_language">#{@best[:memory][:lang]}</span> 
-  with <span class="hof_value">#{number_with_delimiter(@best[:memory][:value])} kbytes </span> 
-  at submission
-  = link_to("#" + @best[:memory][:sub_id].to_s, controller: 'graders' , action: 'submission', id:@best[:memory][:sub_id])
-  %br/
-
-  %b Shortest Code:
-  by #{link_to @best[:length][:user], controller:'users', action:'profile', id:@best[:length][:user_id]} 
-  using <span class="hof_language">#{@best[:length][:lang]}</span> 
-  with  <span class="hof_value">#{@best[:length][:value]} bytes</span> 
-  at submission
-  = link_to("#" + @best[:length][:sub_id].to_s, controller: 'graders' , action: 'submission', id: @best[:length][:sub_id])
-  %br/
-
-  %b First solver:
-  #{link_to @best[:first][:user], controller:'users', action:'profile', id:@best[:first][:user_id]} is the first solver 
-  using <span class="hof_language">#{@best[:first][:lang]}</span> 
-  on <span class="hof_value">#{@best[:first][:value]}</span> 
-  at submission
-  = link_to("#" + @best[:first][:sub_id].to_s, controller: 'graders' , action: 'submission', id: @best[:first][:sub_id])
-  %br/
-
-
-  %p
-    This counts only for submission with 100% score <br/>
-    Right now, java is excluded from memory usage competition. (Because it always uses 2GB memory...)
-
   %h2 By language
 
   %table.info
@@ -75,5 +94,3 @@
               = "(#{value[:first][:value]} @"
               = "#{link_to("#" + value[:first][:sub_id].to_s, controller: 'graders' , action: 'submission', id: value[:first][:sub_id])} )".html_safe
 
-- else
-  %h3 No submissions
diff --git a/app/views/report/problem_hof.html.haml b/app/views/report/problem_hof.html.haml
--- a/app/views/report/problem_hof.html.haml
+++ b/app/views/report/problem_hof.html.haml
@@ -6,7 +6,7 @@
 /  %h1 All-Time Hall of Fame
 
 
-%h1 Tasks Hall of Fame
+%h1 Hall of Fame
 .task-menu
   Tasks
   %br/
@@ -18,5 +18,6 @@
   Please select a problem.
 - else
   =render partial: 'task_hof'
+  %h2 Submission History
+  =render partial: 'application/bar_graph', locals: { histogram: @histogram }
 
-