diff --git a/app.js b/app.js
index f99892f..a55da2b 100644
--- a/app.js
+++ b/app.js
@@ -7,7 +7,7 @@ const fs = require('fs'),
       commandLineArgs = require('command-line-args');
 
 const optionDefinitions = [
-    { name: 'config', alias: 'c', type: String, defaultValue: './config.json' },
+  { name: 'config', alias: 'c', type: String, defaultValue: __dirname + '/config.json' },
 ];
 
 const options = commandLineArgs(optionDefinitions);
@@ -174,7 +174,7 @@ global.syzoj = {
     });
   },
   loadModules() {
-    fs.readdir('./modules/', (err, files) => {
+    fs.readdir(__dirname + '/modules/', (err, files) => {
       if (err) {
         this.log(err);
         return;
@@ -268,4 +268,4 @@ global.syzoj = {
   }
 };
 
-syzoj.run();
+syzoj.untilStarted = syzoj.run();
diff --git a/migrates/build-statistics.js b/migrates/build-statistics.js
new file mode 100644
index 0000000..34daac2
--- /dev/null
+++ b/migrates/build-statistics.js
@@ -0,0 +1,37 @@
+/*
+ * This script will help you build submission_statistics table. SYZOJ changed previous
+ * way of querying every time to cache statistics in database and update it for every
+ * judged submission. Without running this script after migrating will cause old submissions
+ * disappear from statistics.
+ * 
+ */
+
+const fn = async () => {
+  require('..');
+  await syzoj.untilStarted;
+
+  const User = syzoj.model('user');
+  const Problem = syzoj.model('problem');
+  const JudgeState = syzoj.model('judge_state');
+
+  const userIDs = (await User.createQueryBuilder().select('id').getRawMany()).map(record => record.id);
+  for (const id of userIDs) {
+    const problemIDs = (await JudgeState.createQueryBuilder()
+                                        .select('DISTINCT(problem_id)', 'problem_id')
+                                        .where('status = :status', { status: 'Accepted' })
+                                        .andWhere('user_id = :user_id', { user_id: id })
+                                        .andWhere('type = 0')
+                                        .getRawMany()).map(record => record.problem_id);
+    for (const problemID of problemIDs) {
+      const problem = await Problem.findById(problemID);
+      await problem.updateStatistics(id);
+
+      console.log(`userID = ${id}, problemID = ${problemID}`);
+    }
+  }
+
+  process.exit();
+};
+
+// NOTE: Uncomment to run.
+fn();