Solve day 9 and fix horrible bug in lib.

My integer parser did not consider negative values. I have fixed that
in the 2022 repository, but not here. That's pretty annoying.

lib.py

@@ -34,13 +34,13 @@ def lcm(numbers: list[int]) -> int:
 
 def str_to_single_int(line: str) -> int:
     line = line.replace(" ", "")
-    r = re.compile(r"\d+")
+    r = re.compile(r"-?\d+")
     for m in r.findall(line):
         return int(m)
     raise Exception("No single digit sequence in '{line}'")
 
 def str_to_int_list(line: str) -> list[int]:
-    r = re.compile(r"\d+")
+    r = re.compile(r"-?\d+")
     return list(map(int, r.findall(line)))
 
 def str_to_lines_no_empty(text: str) -> list[str]: