diff --git a/.all-contributorsrc b/.all-contributorsrc
index 26bc143b..1536f19b 100644
--- a/.all-contributorsrc
+++ b/.all-contributorsrc
@@ -76,6 +76,15 @@
       "contributions": [
         "code"
       ]
+    },
+    {
+      "login": "sehyun-hwang",
+      "name": "Sehyun Hwang",
+      "avatar_url": "https://avatars3.githubusercontent.com/u/23437715?v=4",
+      "profile": "https://github.com/sehyun-hwang",
+      "contributions": [
+        "maintenance"
+      ]
     }
   ],
   "contributorsPerLine": 7,
diff --git a/README.md b/README.md
index 09d79457..f136228f 100644
--- a/README.md
+++ b/README.md
@@ -4,7 +4,7 @@
 [![Language grade: Python](https://img.shields.io/lgtm/grade/python/g/medipixel/rl_algorithms.svg?logo=lgtm&logoWidth=18)](https://lgtm.com/projects/g/medipixel/rl_algorithms/context:python)
 [![License: MIT](https://img.shields.io/badge/License-MIT-green.svg)](https://opensource.org/licenses/MIT)
 [![Code style: black](https://img.shields.io/badge/code%20style-black-000000.svg)](https://github.com/psf/black)<!-- ALL-CONTRIBUTORS-BADGE:START - Do not remove or modify this section -->
-[![All Contributors](https://img.shields.io/badge/all_contributors-8-orange.svg?style=flat-square)](#contributors-)
+[![All Contributors](https://img.shields.io/badge/all_contributors-9-orange.svg?style=flat-square)](#contributors-)
 <!-- ALL-CONTRIBUTORS-BADGE:END -->
 
 </p>
@@ -36,21 +36,23 @@ Thanks goes to these wonderful people ([emoji key](https://allcontributors.org/d
 <!-- markdownlint-disable -->
 <table>
   <tr>
-    <td align="center"><a href="https://github.com/Curt-Park"><img src="https://avatars3.githubusercontent.com/u/14961526?v=4" width="100px;" alt=""/><br /><sub><b>Jinwoo Park (Curt)</b></sub></a><br /><a href="https://github.com/medipixel/rl_algorithms/commits?author=Curt-Park" title="Code">💻</a></td>
-    <td align="center"><a href="https://github.com/MrSyee"><img src="https://avatars3.githubusercontent.com/u/17582508?v=4" width="100px;" alt=""/><br /><sub><b>Kyunghwan Kim</b></sub></a><br /><a href="https://github.com/medipixel/rl_algorithms/commits?author=MrSyee" title="Code">💻</a></td>
-    <td align="center"><a href="https://github.com/darthegg"><img src="https://avatars3.githubusercontent.com/u/16010242?v=4" width="100px;" alt=""/><br /><sub><b>darthegg</b></sub></a><br /><a href="https://github.com/medipixel/rl_algorithms/commits?author=darthegg" title="Code">💻</a></td>
-    <td align="center"><a href="https://github.com/mclearning2"><img src="https://avatars3.githubusercontent.com/u/43226417?v=4" width="100px;" alt=""/><br /><sub><b>Mincheol Kim</b></sub></a><br /><a href="https://github.com/medipixel/rl_algorithms/commits?author=mclearning2" title="Code">💻</a></td>
-    <td align="center"><a href="https://github.com/minseop4898"><img src="https://avatars1.githubusercontent.com/u/34338299?v=4" width="100px;" alt=""/><br /><sub><b>김민섭</b></sub></a><br /><a href="https://github.com/medipixel/rl_algorithms/commits?author=minseop4898" title="Code">💻</a></td>
-    <td align="center"><a href="https://github.com/jinPrelude"><img src="https://avatars1.githubusercontent.com/u/16518993?v=4" width="100px;" alt=""/><br /><sub><b>Leejin Jung</b></sub></a><br /><a href="https://github.com/medipixel/rl_algorithms/commits?author=jinPrelude" title="Code">💻</a></td>
-    <td align="center"><a href="https://github.com/cyoon1729"><img src="https://avatars2.githubusercontent.com/u/33583101?v=4" width="100px;" alt=""/><br /><sub><b>Chris Yoon</b></sub></a><br /><a href="https://github.com/medipixel/rl_algorithms/commits?author=cyoon1729" title="Code">💻</a></td>
+    <td align="center"><a href="https://github.com/Curt-Park"><img src="https://avatars3.githubusercontent.com/u/14961526?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Jinwoo Park (Curt)</b></sub></a><br /><a href="https://github.com/medipixel/rl_algorithms/commits?author=Curt-Park" title="Code">💻</a></td>
+    <td align="center"><a href="https://github.com/MrSyee"><img src="https://avatars3.githubusercontent.com/u/17582508?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Kyunghwan Kim</b></sub></a><br /><a href="https://github.com/medipixel/rl_algorithms/commits?author=MrSyee" title="Code">💻</a></td>
+    <td align="center"><a href="https://github.com/darthegg"><img src="https://avatars3.githubusercontent.com/u/16010242?v=4?s=100" width="100px;" alt=""/><br /><sub><b>darthegg</b></sub></a><br /><a href="https://github.com/medipixel/rl_algorithms/commits?author=darthegg" title="Code">💻</a></td>
+    <td align="center"><a href="https://github.com/mclearning2"><img src="https://avatars3.githubusercontent.com/u/43226417?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Mincheol Kim</b></sub></a><br /><a href="https://github.com/medipixel/rl_algorithms/commits?author=mclearning2" title="Code">💻</a></td>
+    <td align="center"><a href="https://github.com/minseop4898"><img src="https://avatars1.githubusercontent.com/u/34338299?v=4?s=100" width="100px;" alt=""/><br /><sub><b>김민섭</b></sub></a><br /><a href="https://github.com/medipixel/rl_algorithms/commits?author=minseop4898" title="Code">💻</a></td>
+    <td align="center"><a href="https://github.com/jinPrelude"><img src="https://avatars1.githubusercontent.com/u/16518993?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Leejin Jung</b></sub></a><br /><a href="https://github.com/medipixel/rl_algorithms/commits?author=jinPrelude" title="Code">💻</a></td>
+    <td align="center"><a href="https://github.com/cyoon1729"><img src="https://avatars2.githubusercontent.com/u/33583101?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Chris Yoon</b></sub></a><br /><a href="https://github.com/medipixel/rl_algorithms/commits?author=cyoon1729" title="Code">💻</a></td>
   </tr>
   <tr>
-    <td align="center"><a href="https://jiseonghan.github.io/"><img src="https://avatars2.githubusercontent.com/u/48741026?v=4" width="100px;" alt=""/><br /><sub><b>Jiseong Han</b></sub></a><br /><a href="https://github.com/medipixel/rl_algorithms/commits?author=jiseongHAN" title="Code">💻</a></td>
+    <td align="center"><a href="https://jiseonghan.github.io/"><img src="https://avatars2.githubusercontent.com/u/48741026?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Jiseong Han</b></sub></a><br /><a href="https://github.com/medipixel/rl_algorithms/commits?author=jiseongHAN" title="Code">💻</a></td>
+    <td align="center"><a href="https://github.com/sehyun-hwang"><img src="https://avatars3.githubusercontent.com/u/23437715?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Sehyun Hwang</b></sub></a><br /><a href="#maintenance-sehyun-hwang" title="Maintenance">🚧</a></td>
   </tr>
 </table>
 
-<!-- markdownlint-enable -->
+<!-- markdownlint-restore -->
 <!-- prettier-ignore-end -->
+
 <!-- ALL-CONTRIBUTORS-LIST:END -->
 This project follows the [all-contributors](https://github.com/all-contributors/all-contributors) specification.