diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
index b666e88aa..e60003051 100644
--- a/.pre-commit-config.yaml
+++ b/.pre-commit-config.yaml
@@ -22,6 +22,12 @@ repos:
       - id: isort
         args:
           - --profile=black
+  - repo: https://github.com/asottile/pyupgrade
+    rev: v2.29.0
+    hooks:
+      - id: pyupgrade
+        args:
+          - --py39-plus
   - repo: https://gitlab.com/pycqa/flake8
     rev: 3.9.1
     hooks:
diff --git a/DIRECTORY.md b/DIRECTORY.md
index c94fb78d6..2acfff69d 100644
--- a/DIRECTORY.md
+++ b/DIRECTORY.md
@@ -126,6 +126,7 @@
   * [Molecular Chemistry](https://github.com/TheAlgorithms/Python/blob/master/conversions/molecular_chemistry.py)
   * [Octal To Decimal](https://github.com/TheAlgorithms/Python/blob/master/conversions/octal_to_decimal.py)
   * [Prefix Conversions](https://github.com/TheAlgorithms/Python/blob/master/conversions/prefix_conversions.py)
+  * [Pressure Conversions](https://github.com/TheAlgorithms/Python/blob/master/conversions/pressure_conversions.py)
   * [Rgb Hsv Conversion](https://github.com/TheAlgorithms/Python/blob/master/conversions/rgb_hsv_conversion.py)
   * [Roman Numerals](https://github.com/TheAlgorithms/Python/blob/master/conversions/roman_numerals.py)
   * [Temperature Conversions](https://github.com/TheAlgorithms/Python/blob/master/conversions/temperature_conversions.py)
@@ -860,6 +861,8 @@
     * [Sol1](https://github.com/TheAlgorithms/Python/blob/master/project_euler/problem_301/sol1.py)
   * Problem 551
     * [Sol1](https://github.com/TheAlgorithms/Python/blob/master/project_euler/problem_551/sol1.py)
+  * Problem 686
+    * [Sol1](https://github.com/TheAlgorithms/Python/blob/master/project_euler/problem_686/sol1.py)
 
 ## Quantum
   * [Deutsch Jozsa](https://github.com/TheAlgorithms/Python/blob/master/quantum/deutsch_jozsa.py)
diff --git a/data_structures/binary_tree/merge_two_binary_trees.py b/data_structures/binary_tree/merge_two_binary_trees.py
index 748726894..3380f8c5f 100644
--- a/data_structures/binary_tree/merge_two_binary_trees.py
+++ b/data_structures/binary_tree/merge_two_binary_trees.py
@@ -7,8 +7,6 @@ will be used as the node of new tree.
 """
 from __future__ import annotations
 
-from typing import Optional
-
 
 class Node:
     """
@@ -21,7 +19,7 @@ class Node:
         self.right: Node | None = None
 
 
-def merge_two_binary_trees(tree1: Node | None, tree2: Node | None) -> Optional[Node]:
+def merge_two_binary_trees(tree1: Node | None, tree2: Node | None) -> Node | None:
     """
     Returns root node of the merged tree.
 
diff --git a/data_structures/linked_list/skip_list.py b/data_structures/linked_list/skip_list.py
index be30592ec..176049120 100644
--- a/data_structures/linked_list/skip_list.py
+++ b/data_structures/linked_list/skip_list.py
@@ -5,14 +5,14 @@ https://epaperpress.com/sortsearch/download/skiplist.pdf
 from __future__ import annotations
 
 from random import random
-from typing import Generic, Optional, TypeVar, Union
+from typing import Generic, TypeVar
 
 KT = TypeVar("KT")
 VT = TypeVar("VT")
 
 
 class Node(Generic[KT, VT]):
-    def __init__(self, key: Union[KT, str] = "root", value: Optional[VT] = None):
+    def __init__(self, key: KT | str = "root", value: VT | None = None):
         self.key = key
         self.value = value
         self.forward: list[Node[KT, VT]] = []