diff --git a/2021/day6.py b/2021/day6.py
new file mode 100644
index 0000000..3399353
--- /dev/null
+++ b/2021/day6.py
@@ -0,0 +1,35 @@
+import sys
+
+
+def main():
+    lines = [line.rstrip() for line in sys.stdin]
+    data = {k: 0 for k in range(1, 6)}
+    for n in map(int, lines[0].split(",")):
+        data[n] += 1
+
+    # Part 1
+    for _ in range(80):
+        data = step(data)
+    print(sum(data.values()))
+
+    # Part 2
+    for _ in range(256 - 80):
+        data = step(data)
+    print(sum(data.values()))
+
+
+def step(data):
+    next_data = {k: 0 for k in range(1, 9)}
+    for k, v in data.items():
+        if v == 0:
+            continue
+        if k == 0:
+            next_data[6] += v
+            next_data[8] += v
+        else:
+            next_data[k - 1] = v
+    return next_data
+
+
+if __name__ == "__main__":
+    main()