diff --git a/package.json b/package.json
index d528be034..485e95a4e 100644
--- a/package.json
+++ b/package.json
@@ -27,7 +27,7 @@
         "globby": "^11.0.1",
         "jest": "^26.2.2",
         "latest-version": "^5.1.0",
-        "ora": "^4.0.5",
+        "ora": "^5.0.0",
         "semver": "^7.3.2",
         "ts-jest": "^26.1.4",
         "typescript": "^3.9.7"
diff --git a/packages/hydrooj/TODO b/packages/hydrooj/TODO
index a670000cd..c448fc491 100644
--- a/packages/hydrooj/TODO
+++ b/packages/hydrooj/TODO
@@ -4,6 +4,4 @@ SETTINGS_PRIVACY.allowRegisteredUsers
 model.setting.ui.name
 pdoc.secretConfig?
 message.markAsRead
-批量导入用户
-domain_join_application
-problem.difficulty_setting
\ No newline at end of file
+domain_join_application
\ No newline at end of file
diff --git a/packages/hydrooj/package.json b/packages/hydrooj/package.json
index 212f05320..87cd17cac 100644
--- a/packages/hydrooj/package.json
+++ b/packages/hydrooj/package.json
@@ -1,6 +1,6 @@
 {
     "name": "hydrooj",
-    "version": "2.12.5",
+    "version": "2.12.6",
     "bin": "bin/hydrooj.js",
     "main": "dist/loader.js",
     "typings": "dist/loader.d.ts",
@@ -35,7 +35,7 @@
         "mongodb": "^3.5.9",
         "nodemailer": "^6.4.10",
         "nunjucks": "^3.2.2",
-        "prismjs": "^1.20.0",
+        "prismjs": "^1.21.0",
         "proxy-agent": "^3.1.1",
         "ps-list": "^7.2.0",
         "serialize-javascript": "^4.0.0",
diff --git a/packages/hydrooj/src/entry/common.ts b/packages/hydrooj/src/entry/common.ts
index 87867954a..0cb2b4052 100644
--- a/packages/hydrooj/src/entry/common.ts
+++ b/packages/hydrooj/src/entry/common.ts
@@ -26,7 +26,7 @@ export const builtinHandler = [
 ];
 
 export const builtinScript = [
-    'rating', 'register', 'problemStat', 'blacklist', 'deleteUser',
+    'rating', 'difficulty', 'problemStat', 'blacklist', 'deleteUser',
     'upgrade0_1',
 ];
 
diff --git a/packages/hydrooj/src/handler/manage.ts b/packages/hydrooj/src/handler/manage.ts
index ac4980278..388a0c7e5 100644
--- a/packages/hydrooj/src/handler/manage.ts
+++ b/packages/hydrooj/src/handler/manage.ts
@@ -165,6 +165,7 @@ class SystemSettingHandler extends SystemHandler {
 class SystemUserImportHandler extends SystemHandler {
     async get() {
         this.response.body.users = [];
+        this.response.body.path.push(['manage_user_import']);
         this.response.template = 'manage_user_import.html';
     }
 
@@ -188,7 +189,9 @@ class SystemUserImportHandler extends SystemHandler {
                 }
             } else messages.push(`Line ${i + 1}: Input invalid.`);
         }
+        messages.push(`${udocs.length} users found.`);
         await Promise.all(tasks);
+        this.response.body.path.push(['manage_user_import']);
         this.response.body.users = udocs;
         this.response.body.messages = messages;
     }
diff --git a/packages/hydrooj/src/handler/problem.ts b/packages/hydrooj/src/handler/problem.ts
index 5294b2247..0ae21d130 100644
--- a/packages/hydrooj/src/handler/problem.ts
+++ b/packages/hydrooj/src/handler/problem.ts
@@ -369,12 +369,23 @@ class ProblemSettingsHandler extends ProblemManageHandler {
     @param('hidden', Types.Boolean)
     @param('category', Types.String, true, null, parseCategory)
     @param('tag', Types.String, true, null, parseCategory)
+    @param('difficultySetting', Types.UnsignedInt)
+    @param('difficultyAdmin', Types.UnsignedInt, true)
     async postSetting(
         domainId: string, pid: string | number, hidden = false,
         category: string[] = [], tag: string[] = [],
+        difficultySetting: string, difficultyAdmin: number,
     ) {
         const pdoc = await problem.get(domainId, pid);
-        await problem.edit(domainId, pdoc.docId, { hidden, category, tag });
+        if (!problem.SETTING_DIFFICULTY_RANGE[difficultySetting]) {
+            throw new ValidationError('difficultySetting');
+        }
+        if (!difficultyAdmin) difficultyAdmin = null;
+        else if (difficultyAdmin < 1 || difficultyAdmin > 9) throw new ValidationError('difficultyAdmin');
+        await problem.edit(domainId, pdoc.docId, {
+            hidden, category, tag, difficultySetting, difficultyAdmin,
+        });
+        await global.Hydro.script.difficulty.run({ domainId, pid }, console.log);
         this.back();
     }
 }
diff --git a/packages/hydrooj/src/interface.ts b/packages/hydrooj/src/interface.ts
index ee30309d3..0d0fa8ec9 100644
--- a/packages/hydrooj/src/interface.ts
+++ b/packages/hydrooj/src/interface.ts
@@ -135,11 +135,15 @@ export interface Pdoc {
     nAccept: number,
     tag: string[],
     category: string[],
-    difficulty: number,
     data?: ProblemData,
     hidden: boolean,
     config: ProblemConfig,
     acMsg?: string,
+
+    difficulty?: number,
+    difficultyAlgo?: number,
+    difficultyAdmin?: number,
+    difficultySetting?: number,
 }
 
 export type Pdict = NumericDictionary<Pdoc>;
diff --git a/packages/hydrooj/src/model/problem.ts b/packages/hydrooj/src/model/problem.ts
index bed24de83..77fcbb04a 100644
--- a/packages/hydrooj/src/model/problem.ts
+++ b/packages/hydrooj/src/model/problem.ts
@@ -10,6 +10,16 @@ import {
 import { ProblemNotFoundError } from '../error';
 import * as testdataConfig from '../lib/testdataConfig';
 
+export const SETTING_DIFFICULTY_ALGORITHM = 0;
+export const SETTING_DIFFICULTY_ADMIN = 1;
+export const SETTING_DIFFICULTY_AVERAGE = 2;
+
+export const SETTING_DIFFICULTY_RANGE = [
+    [SETTING_DIFFICULTY_ALGORITHM, 'Use algorithm calculated'],
+    [SETTING_DIFFICULTY_ADMIN, 'Use admin specificed'],
+    [SETTING_DIFFICULTY_AVERAGE, 'Use average of above'],
+];
+
 export const pdocHidden: Pdoc = {
     _id: new ObjectID(),
     domainId: 'system',
@@ -152,6 +162,11 @@ export async function setTestdata(domainId: string, _id: number, filePath: strin
 }
 
 global.Hydro.model.problem = {
+    SETTING_DIFFICULTY_ADMIN,
+    SETTING_DIFFICULTY_ALGORITHM,
+    SETTING_DIFFICULTY_AVERAGE,
+    SETTING_DIFFICULTY_RANGE,
+
     pdocHidden,
     add,
     inc,
diff --git a/packages/hydrooj/src/script/difficulty.ts b/packages/hydrooj/src/script/difficulty.ts
new file mode 100644
index 000000000..c44d03e69
--- /dev/null
+++ b/packages/hydrooj/src/script/difficulty.ts
@@ -0,0 +1,73 @@
+import { Pdoc } from '../interface';
+import * as problem from '../model/problem';
+
+export const description = 'Create a new user';
+
+const _CACHE_INFO = {
+    last_s: 0.0,
+    last_y: 0,
+    values: [0.0],
+};
+
+function _LOGP(x: number) {
+    const sqrt_2_pi = 2.506628274631000502415765284811; // Sqrt[Pi]
+    return (2 * Math.exp(-1.0 * (Math.log(x) ** 2) * 2)) / x / sqrt_2_pi;
+}
+
+function _integrate_ensure_cache(y: number) {
+    let last_y = _CACHE_INFO.last_y;
+    if (y <= last_y) return _CACHE_INFO;
+    let s = _CACHE_INFO.last_s;
+    const dx = 0.1;
+    const dT = 2;
+    let x0 = (last_y / dT) * dx;
+    while (y > last_y) {
+        x0 += dx;
+        s += _LOGP(x0) * dx;
+        for (let i = 1; i <= dT; i++) _CACHE_INFO.values.push(s);
+        last_y += dT;
+    }
+    _CACHE_INFO.last_y = last_y;
+    _CACHE_INFO.last_s = s;
+    return _CACHE_INFO;
+}
+
+_integrate_ensure_cache(1000000);
+
+function _integrate(y: number) {
+    _integrate_ensure_cache(y);
+    return _CACHE_INFO.values[y];
+}
+
+function difficultyAlgorithm(nSubmit: number, nAccept: number) {
+    if (!nSubmit) return null;
+    const s = _integrate(nSubmit);
+    const ac_rate = nAccept / nSubmit;
+    const ans = Math.round(10.0 - 1.30 * s * 10.0 * ac_rate);
+    return Math.max(ans, 1);
+}
+
+function _get_difficulty(pdoc: Pdoc, calculatedDifficulty: number) {
+    const setting = pdoc.difficultySetting;
+    if (setting === problem.SETTING_DIFFICULTY_ALGORITHM) return calculatedDifficulty;
+    if (setting === problem.SETTING_DIFFICULTY_ADMIN) return pdoc.difficultyAdmin;
+    if (setting === problem.SETTING_DIFFICULTY_AVERAGE && pdoc.difficultyAdmin !== null) {
+        return Math.round((calculatedDifficulty + pdoc.difficultyAdmin) / 2);
+    } return calculatedDifficulty;
+}
+
+export async function run({
+    domainId, pid,
+}) {
+    const pdoc = await problem.get(domainId, pid);
+    const difficultyAlgo = difficultyAlgorithm(pdoc.nSubmit, pdoc.nAccept);
+    const difficulty = _get_difficulty(pdoc, difficultyAlgo);
+    return await problem.edit(domainId, pdoc.docId, { difficulty, difficultyAlgo });
+}
+
+export const validate = {
+    domainId: { $type: 'string' },
+    pid: { $type: 'number' },
+};
+
+global.Hydro.script.difficulty = { run, description, validate };
diff --git a/packages/hydrooj/src/script/register.ts b/packages/hydrooj/src/script/register.ts
deleted file mode 100644
index c9ff877ed..000000000
--- a/packages/hydrooj/src/script/register.ts
+++ /dev/null
@@ -1,20 +0,0 @@
-import * as user from '../model/user';
-
-export const description = 'Create a new user';
-
-export async function run({
-    uname, password, mail, uid,
-}) {
-    if (uid) uid = parseInt(uid, 10);
-    if (uid && Number.isNaN(uid)) throw new Error('uid');
-    uid = await user.create(mail, uname, password, uid);
-    return uid;
-}
-
-export const validate = {
-    uname: { $type: 'string' },
-    password: { $type: 'string' },
-    mail: { $type: 'string' },
-};
-
-global.Hydro.script.register = { run, description, validate };