diff --git a/reasoning_gym/algorithmic/__init__.py b/reasoning_gym/algorithmic/__init__.py
index 20f3e90c..2400f49c 100644
--- a/reasoning_gym/algorithmic/__init__.py
+++ b/reasoning_gym/algorithmic/__init__.py
@@ -24,10 +24,10 @@ from .rotate_matrix import RotateMatrixConfig, RotateMatrixDataset
 from .sentence_reordering import SentenceReorderingConfig, SentenceReorderingDataset
 from .spell_backward import SpellBackwardConfig, SpellBackwardDataset
 from .spiral_matrix import SpiralMatrixConfig, SpiralMatrixDataset
+from .string_insertion import StringInsertionConfig, StringInsertionDataset
 from .word_ladder import WordLadderConfig, WordLadderDataset
 from .word_sequence_reversal import WordSequenceReversalConfig, WordSequenceReversalDataset
 from .word_sorting import TextTransformation, WordSortingConfig, WordSortingDataset
-from .string_insertion import StringInsertionConfig, StringInsertionDataset
 
 __all__ = [
     "SpellBackwardConfig",
diff --git a/reasoning_gym/algorithmic/string_insertion.py b/reasoning_gym/algorithmic/string_insertion.py
index fb1d35e0..b217ed76 100644
--- a/reasoning_gym/algorithmic/string_insertion.py
+++ b/reasoning_gym/algorithmic/string_insertion.py
@@ -9,7 +9,6 @@ from typing import Optional
 
 from ..factory import ProceduralDataset, register_dataset
 
-
 QUESTION_TEMPLATE = """Given a string consisting of characters A, B, C, D, and E, your job is to insert a character according to the following pattern:
 1. If there is a substring ABCD in the string, insert the character A after the substring.
 2. If there is a substring BCDE in the string, insert the character B after the substring.
@@ -22,7 +21,7 @@ Once you have inserted a character, you have to skip over the substring and the
 Example
 - Input: DDABCDEEDEAB
 - Output: DDABCDAEEDEABD
-- Explanation: 
+- Explanation:
     - Theere are two inserted characters: DDABCD[A]EEDEAB[D] (shown in square brackets)
     - First, we insert A after ABCD.
     - Even though with the newly inserted 'A' we can obtain the substring BCD[A], we can't use it to insert another character.
@@ -37,7 +36,7 @@ class StringInsertionConfig:
     """Configuration for String Insertion dataset generation"""
 
     min_string_length: int = 5  # Minimum string length
-    max_string_length: int = 20 # Maximum string length
+    max_string_length: int = 20  # Maximum string length
 
     size: int = 500  # Virtual dataset size
     seed: Optional[int] = None
@@ -47,12 +46,13 @@ class StringInsertionConfig:
         assert 5 <= self.min_string_length, "Minimum string length should be at least 5"
         assert self.min_string_length <= self.max_string_length, "Minimum string length should be less than maximum"
 
+
 class StringInsertionDataset(ProceduralDataset):
     """Generates String Insertion exercises with configurable difficulty"""
 
     def __init__(self, config: StringInsertionConfig):
         super().__init__(config=config, seed=config.seed, size=config.size)
-        self.vocabulary = ['A', 'B', 'C', 'D', 'E']
+        self.vocabulary = ["A", "B", "C", "D", "E"]
         self.insertion_rules = [
             ("ABCD", "A"),
             ("BCDE", "B"),
@@ -68,7 +68,7 @@ class StringInsertionDataset(ProceduralDataset):
         while i < len(string):
             inserted = False
             for pattern, char in self.insertion_rules:
-                substring = string[i:i+len(pattern)]
+                substring = string[i : i + len(pattern)]
                 if substring == pattern:
                     output.append(substring + char)
                     i += len(pattern)
@@ -82,7 +82,7 @@ class StringInsertionDataset(ProceduralDataset):
     def __getitem__(self, idx: int) -> dict:
         """Generate a single String Insertion question"""
         rng = Random(self.seed + idx)
-        
+
         string_length = rng.randint(self.config.min_string_length, self.config.max_string_length)
         string = [rng.choice(self.vocabulary) for _ in range(string_length)]
 
diff --git a/tests/test_string_insertion.py b/tests/test_string_insertion.py
index 746ff5c5..12225954 100644
--- a/tests/test_string_insertion.py
+++ b/tests/test_string_insertion.py
@@ -7,13 +7,13 @@ from reasoning_gym.algorithmic.string_insertion import StringInsertionConfig, St
 
 def test_string_insertion_config_validation():
     """Test that invalid configs raise appropriate errors"""
-    
+
     for field in ["min_string_length", "max_string_length"]:
         for i in range(-1, 5):
             with pytest.raises(AssertionError):
-                config = StringInsertionConfig(**{field: i}) # [-1, 4] is invalid
+                config = StringInsertionConfig(**{field: i})  # [-1, 4] is invalid
                 config.validate()
-    
+
 
 def test_string_insertion_dataset_deterministic():
     """Test that dataset generates same items with same seed"""
@@ -67,7 +67,7 @@ def test_string_insertion_answer():
     config = StringInsertionConfig(seed=42)
     dataset = StringInsertionDataset(config)
 
-    # No pattern match 
+    # No pattern match
     assert dataset._get_answer("AAAAAAA") == "AAAAAAA"
     assert dataset._get_answer("ADBEEBEA") == "ADBEEBEA"
     assert dataset._get_answer("ADEACA") == "ADEACA"
@@ -91,4 +91,4 @@ def test_string_insertion_answer():
     assert dataset._get_answer("AABCDEEEEEEEBCDEAAAAA") == "AABCDAEEEEEEEBCDEBAAAAA"
 
     # No reuse of newly inserted characters
-    assert dataset._get_answer("ABCDBCD") == "ABCDABCD"
\ No newline at end of file
+    assert dataset._get_answer("ABCDBCD") == "ABCDABCD"