diff --git a/2019/d18/ex1/ex1.py b/2019/d18/ex1/ex1.py
index 1968be5..8599ea4 100755
--- a/2019/d18/ex1/ex1.py
+++ b/2019/d18/ex1/ex1.py
@@ -65,7 +65,7 @@ def build_graph(grid: RawGrid) -> Graph:
 
 
 def solve(G: Graph, start: str) -> int:
-    @lru_cache(2 ** 20)
+    @lru_cache(2**20)
     def reachable_keys(src: str, found: FrozenSet[str]) -> List[Tuple[str, int]]:
         queue = []
         distance: DefaultDict[str, Union[float, int]] = defaultdict(lambda: inf)
@@ -97,7 +97,7 @@ def solve(G: Graph, start: str) -> int:
 
         return reachable
 
-    @lru_cache(2 ** 20)
+    @lru_cache(2**20)
     def min_steps(
         src: str, keys_to_find: int, found: FrozenSet[str] = frozenset()
     ) -> int:
diff --git a/2019/d18/ex2/ex2.py b/2019/d18/ex2/ex2.py
index 4463618..9b890a5 100755
--- a/2019/d18/ex2/ex2.py
+++ b/2019/d18/ex2/ex2.py
@@ -65,7 +65,7 @@ def build_graph(grid: RawGrid) -> Graph:
 
 
 def solve(G: Graph, start: str) -> int:
-    @lru_cache(2 ** 20)
+    @lru_cache(2**20)
     def reachable_keys(src: str, found: FrozenSet[str]) -> GraphInfo:
         queue = []
         distance: DefaultDict[str, Union[float, int]] = defaultdict(lambda: inf)
@@ -97,7 +97,7 @@ def solve(G: Graph, start: str) -> int:
 
         return reachable
 
-    @lru_cache(2 ** 20)
+    @lru_cache(2**20)
     def min_steps(
         sources: str, keys_to_find: int, found: FrozenSet[str] = frozenset()
     ) -> Union[float, int]:
diff --git a/flake.lock b/flake.lock
index b743e83..7bc7877 100644
--- a/flake.lock
+++ b/flake.lock
@@ -1,12 +1,28 @@
 {
   "nodes": {
+    "flake-compat": {
+      "flake": false,
+      "locked": {
+        "lastModified": 1668681692,
+        "narHash": "sha256-Ht91NGdewz8IQLtWZ9LCeNXMSXHUss+9COoqu6JLmXU=",
+        "owner": "edolstra",
+        "repo": "flake-compat",
+        "rev": "009399224d5e398d03b22badca40a37ac85412a1",
+        "type": "github"
+      },
+      "original": {
+        "owner": "edolstra",
+        "repo": "flake-compat",
+        "type": "github"
+      }
+    },
     "futils": {
       "locked": {
-        "lastModified": 1638122382,
-        "narHash": "sha256-sQzZzAbvKEqN9s0bzWuYmRaA03v40gaJ4+iL1LXjaeI=",
+        "lastModified": 1667395993,
+        "narHash": "sha256-nuEHfE/LcWyuSWnS8t12N1wc105Qtau+/OdUAjtQ0rA=",
         "owner": "numtide",
         "repo": "flake-utils",
-        "rev": "74f7e4319258e287b0f9cb95426c9853b282730b",
+        "rev": "5aed5285a952e0b949eb3ba02c12fa4fcfef535f",
         "type": "github"
       },
       "original": {
@@ -16,13 +32,34 @@
         "type": "github"
       }
     },
+    "gitignore": {
+      "inputs": {
+        "nixpkgs": [
+          "pre-commit-hooks",
+          "nixpkgs"
+        ]
+      },
+      "locked": {
+        "lastModified": 1660459072,
+        "narHash": "sha256-8DFJjXG8zqoONA1vXtgeKXy68KdJL5UaXR8NtVMUbx8=",
+        "owner": "hercules-ci",
+        "repo": "gitignore.nix",
+        "rev": "a20de23b925fd8264fd7fad6454652e142fd7f73",
+        "type": "github"
+      },
+      "original": {
+        "owner": "hercules-ci",
+        "repo": "gitignore.nix",
+        "type": "github"
+      }
+    },
     "nixpkgs": {
       "locked": {
-        "lastModified": 1638286143,
-        "narHash": "sha256-A+rgjbIpz3uPRKHPXwdmouVcVn5pZqLnaZHymjkraG4=",
+        "lastModified": 1669542132,
+        "narHash": "sha256-DRlg++NJAwPh8io3ExBJdNW7Djs3plVI5jgYQ+iXAZQ=",
         "owner": "NixOS",
         "repo": "nixpkgs",
-        "rev": "29d1f6e1f625d246dcf84a78ef97b4da3cafc6ea",
+        "rev": "a115bb9bd56831941be3776c8a94005867f316a7",
         "type": "github"
       },
       "original": {
@@ -34,19 +71,24 @@
     },
     "pre-commit-hooks": {
       "inputs": {
+        "flake-compat": "flake-compat",
         "flake-utils": [
           "futils"
         ],
+        "gitignore": "gitignore",
         "nixpkgs": [
           "nixpkgs"
+        ],
+        "nixpkgs-stable": [
+          "nixpkgs"
         ]
       },
       "locked": {
-        "lastModified": 1637745948,
-        "narHash": "sha256-DmQG1bZk24eS+BAHwnHPyYIadMLKbq0d1b//iapYIPU=",
+        "lastModified": 1669829516,
+        "narHash": "sha256-laWMD/TZzyrulu8xLNoSPertXOxjRD7BrcAVwKl+NyQ=",
         "owner": "cachix",
         "repo": "pre-commit-hooks.nix",
-        "rev": "c3b4f94350b0e59c2546fa85890cc70d03616b9c",
+        "rev": "471c7f1ecace25e39099206431300322632d25c4",
         "type": "github"
       },
       "original": {
diff --git a/flake.nix b/flake.nix
index 7796816..d09ee81 100644
--- a/flake.nix
+++ b/flake.nix
@@ -24,6 +24,7 @@
       inputs = {
         flake-utils.follows = "futils";
         nixpkgs.follows = "nixpkgs";
+        nixpkgs-stable.follows = "nixpkgs";
       };
     };
   };