diff --git a/2016/d25/ex1/ex1.py b/2016/d25/ex1/ex1.py
new file mode 100755
index 0000000..cd53244
--- /dev/null
+++ b/2016/d25/ex1/ex1.py
@@ -0,0 +1,48 @@
+#!/usr/bin/env python
+
+import enum
+import sys
+from typing import NamedTuple
+
+
+class Op(enum.StrEnum):
+    CPY = "cpy"
+    INC = "inc"
+    DEC = "dec"
+    JNZ = "jnz"
+    OUT = "out"
+
+
+class Instruction(NamedTuple):
+    op: Op
+    x: str
+    y: str | None = None
+
+    @classmethod
+    def from_str(cls, input: str) -> "Instruction":
+        op, *rest = input.split()
+        return cls(Op(op), *rest)
+
+
+def solve(input: str) -> int:
+    def parse(input: str) -> list[Instruction]:
+        return [Instruction.from_str(line) for line in input.splitlines()]
+
+    def next_signal_int(n: int) -> int:
+        res = 0b10
+        while res < n:
+            res = (res << 2) | res
+        return res
+
+    instructions = parse(input)
+    bc = int(instructions[1].x) * int(instructions[2].x)
+    return next_signal_int(bc) - bc
+
+
+def main() -> None:
+    input = sys.stdin.read()
+    print(solve(input))
+
+
+if __name__ == "__main__":
+    main()