diff --git a/day09/part3.py b/day09/part3.py
new file mode 100644
index 0000000..576d0cb
--- /dev/null
+++ b/day09/part3.py
@@ -0,0 +1,20 @@
+#!/usr/bin/env python3
+import math
+from math import comb
+
+from tqdm import tqdm
+
+lines = (x.strip() for x in open("input.txt"))
+result = 0
+
+for line in tqdm(lines, total=200):
+    numbers = [int(x) for x in line.split(" ")]
+    combinations = [((idx+len(numbers))%2*2-1) * comb(len(numbers), idx) for idx in range(len(numbers))]
+    for _ in range(365*5):
+        numbers.append(sum(factor*val for factor, val in zip(combinations, numbers)))
+        combinations.append(-1)
+        combinations = [-combinations[0] if i == 0 else combinations[i-1]-combinations[i] for i in range(len(combinations))]
+    result += numbers[-1]
+
+print(result)
+print(result == 209183938389133193643668550962121882909751535)