diff --git a/2022/d21/ex1/ex1.py b/2022/d21/ex1/ex1.py
new file mode 100755
index 0000000..7c12836
--- /dev/null
+++ b/2022/d21/ex1/ex1.py
@@ -0,0 +1,80 @@
+#!/usr/bin/env python
+
+import dataclasses
+import enum
+import operator
+import sys
+from typing import Optional
+
+
+class Operator(str, enum.Enum):
+    ADD = "+"
+    SUB = "-"
+    MUL = "*"
+    DIV = "/"
+
+    def __call__(self, lhs: int, rhs: int) -> int:
+        OPERATIONS = {
+            self.ADD: operator.add,
+            self.SUB: operator.sub,
+            self.MUL: operator.mul,
+            self.DIV: operator.floordiv,
+        }
+        return OPERATIONS[self](lhs, rhs)
+
+
+class Monkey:
+    def get_value(self, monkeys: dict[str, "Monkey"]) -> int:
+        raise NotImplemented
+
+
+@dataclasses.dataclass
+class YellerMonkey(Monkey):
+    value: int
+
+    def get_value(self, monkeys: dict[str, "Monkey"]) -> int:
+        return self.value
+
+
+@dataclasses.dataclass
+class MathMonkey(Monkey):
+    lhs: str
+    op: Operator
+    rhs: str
+    _value: Optional[int] = dataclasses.field(default=None, init=False)
+
+    def get_value(self, monkeys: dict[str, "Monkey"]) -> int:
+        if self._value is None:
+            self._value = self.op(
+                monkeys[self.lhs].get_value(monkeys),
+                monkeys[self.rhs].get_value(monkeys),
+            )
+        return self._value
+
+
+def solve(input: list[str]) -> int:
+    def parse_monkey(input: str) -> tuple[str, Monkey]:
+        name, value = input.split(": ")
+
+        monkey: Monkey
+        match value.split():
+            case [lhs, op, rhs]:
+                monkey = MathMonkey(lhs, Operator(op), rhs)
+            case [n]:
+                monkey = YellerMonkey(int(n))
+            case _:
+                assert False  # Sanity check
+
+        return name, monkey
+
+    monkeys = dict(map(parse_monkey, input))
+    return monkeys["root"].get_value(monkeys)
+
+
+def main() -> None:
+    input = sys.stdin.read().splitlines()
+    print(solve(input))
+
+
+if __name__ == "__main__":
+    main()