diff --git a/src/holt59/aoc/2015/day11.py b/src/holt59/aoc/2015/day11.py
new file mode 100644
index 0000000..16c553b
--- /dev/null
+++ b/src/holt59/aoc/2015/day11.py
@@ -0,0 +1,50 @@
+import itertools
+import sys
+
+
+def is_valid(p: str) -> bool:
+    if any(c in "iol" for c in p):
+        return False
+
+    if not any(
+        ord(a) + 1 == ord(b) and ord(b) + 1 == ord(c)
+        for a, b, c in zip(p, p[1:], p[2:])
+    ):
+        return False
+
+    if sum(len(list(g)) >= 2 for _, g in itertools.groupby(p)) < 2:
+        return False
+
+    return True
+
+
+assert not is_valid("hijklmmn")
+assert not is_valid("abbceffg")
+assert not is_valid("abbcegjk")
+assert is_valid("abcdffaa")
+assert is_valid("ghjaabcc")
+
+
+def increment(p: str) -> str:
+    if p[-1] == "z":
+        return increment(p[:-1]) + "a"
+    elif p[-1] in "iol":
+        return p[:-1] + chr(ord(p[-1]) + 2)
+    else:
+        return p[:-1] + chr(ord(p[-1]) + 1)
+
+
+def find_next_password(p: str) -> str:
+    while not is_valid(p):
+        p = increment(p)
+    return p
+
+
+line = sys.stdin.read().strip()
+
+
+answer_1 = find_next_password(line)
+print(f"answer 1 is {answer_1}")
+
+answer_2 = find_next_password(increment(answer_1))
+print(f"answer 2 is {answer_2}")
diff --git a/src/holt59/aoc/inputs/holt59/2015/day11.txt b/src/holt59/aoc/inputs/holt59/2015/day11.txt
new file mode 100644
index 0000000..5915be7
--- /dev/null
+++ b/src/holt59/aoc/inputs/holt59/2015/day11.txt
@@ -0,0 +1 @@
+cqjxjnds