Update DIRECTORY.md

Author: Rohanrbharadwaj

DIRECTORY.md

@@ -854,6 +854,8 @@
     * [Sol1](https://github.com/TheAlgorithms/Python/blob/master/project_euler/problem_135/sol1.py)
   * Problem 144
     * [Sol1](https://github.com/TheAlgorithms/Python/blob/master/project_euler/problem_144/sol1.py)
+  * Problem 145
+    * [Sol1](https://github.com/TheAlgorithms/Python/blob/master/project_euler/problem_145/sol1.py)
   * Problem 173
     * [Sol1](https://github.com/TheAlgorithms/Python/blob/master/project_euler/problem_173/sol1.py)
   * Problem 174