diff --git a/2015/d23/ex1/ex1.py b/2015/d23/ex1/ex1.py
new file mode 100755
index 0000000..b498706
--- /dev/null
+++ b/2015/d23/ex1/ex1.py
@@ -0,0 +1,67 @@
+#!/usr/bin/env python
+
+import enum
+import sys
+from typing import NamedTuple
+
+
+class Op(enum.StrEnum):
+    HLF = "hlf"
+    TPL = "tpl"
+    INC = "inc"
+    JMP = "jmp"
+    JIE = "jie"
+    JIO = "jio"
+
+
+class Instruction(NamedTuple):
+    op: Op
+    x: str
+    y: str | None = None
+
+    @classmethod
+    def from_str(cls, input: str) -> "Instruction":
+        op, rest = input.split(None, 1)
+        return cls(Op(op), *rest.split(", "))
+
+
+def solve(input: str) -> int:
+    def parse(input: str) -> list[Instruction]:
+        return [Instruction.from_str(line) for line in input.splitlines()]
+
+    instructions = parse(input)
+    registers: dict[str, int] = {"a": 0, "b": 0}
+
+    ip = 0
+    while True:
+        if ip < 0 or ip >= len(instructions):
+            break
+        instr = instructions[ip]
+        ip += 1
+        match instr.op:
+            case Op.HLF:
+                registers[instr.x] //= 2
+            case Op.TPL:
+                registers[instr.x] *= 3
+            case Op.INC:
+                registers[instr.x] += 1
+            case Op.JMP:
+                ip += int(instr.x) - 1  # Account auto-increment
+            case Op.JIE:
+                assert instr.y is not None
+                if registers[instr.x] % 2 == 0:
+                    ip += int(instr.y) - 1  # Account auto-increment
+            case Op.JIO:
+                assert instr.y is not None
+                if registers[instr.x] == 1:
+                    ip += int(instr.y) - 1  # Account auto-increment
+    return registers["b"]
+
+
+def main() -> None:
+    input = sys.stdin.read()
+    print(solve(input))
+
+
+if __name__ == "__main__":
+    main()