diff --git a/DIRECTORY.md b/DIRECTORY.md
index af150b12984b..aa9bd313b898 100644
--- a/DIRECTORY.md
+++ b/DIRECTORY.md
@@ -740,6 +740,7 @@
   * [Tower Of Hanoi](other/tower_of_hanoi.py)
 
 ## Physics
+  * [Altitude Pressure](physics/altitude_pressure.py)
   * [Archimedes Principle](physics/archimedes_principle.py)
   * [Basic Orbital Capture](physics/basic_orbital_capture.py)
   * [Casimir Effect](physics/casimir_effect.py)
diff --git a/maths/collatz_sequence.py b/maths/collatz_sequence.py
index 4f3aa5582731..b47017146a1e 100644
--- a/maths/collatz_sequence.py
+++ b/maths/collatz_sequence.py
@@ -57,7 +57,7 @@ def collatz_sequence(n: int) -> Generator[int, None, None]:
 
 
 def main():
-    n = 43
+    n = int(input("Your number: "))
     sequence = tuple(collatz_sequence(n))
     print(sequence)
     print(f"Collatz sequence from {n} took {len(sequence)} steps.")