diff --git a/d11/run.py b/d11/run.py
new file mode 100644
index 0000000..d5741dc
--- /dev/null
+++ b/d11/run.py
@@ -0,0 +1,40 @@
+import sys
+
+letters = 'abcdefghijklmnopqrstuvwxyz'
+doubles = [c+c for c in letters]
+straights = [a+b+c for a,b,c in zip(letters, letters[1:], letters[2:])]
+next_letter = {c1: c2 for c1, c2 in zip(letters, letters[1:]+'a')}
+
+
+def is_valid(s):
+    # cannot contain i, o, or l
+    if 'i' in s or 'o' in s or 'l' in s:
+        return False
+    # must include two different pairs of letters
+    if sum([d in s for d in doubles]) < 2:
+        return False
+    # must include a straight of length 3 or greater
+    if not any([d in s for d in straights]):
+        return False
+    return True
+
+
+def next_password(s):
+    s = s[:-1] + next_letter[s[-1]]  # increment the last letter
+    for i in range(-1, -8, -1):
+        if s[i] == 'a':  # increment n-1 letter is n letter changed to 'a'
+            s = s[:i-1] + next_letter[s[i-1]] + s[i:]
+        else:
+            break
+    return s
+
+
+password = sys.argv[1]
+while not is_valid(password):
+    password = next_password(password)
+print(password)
+
+password = next_password(password)
+while not is_valid(password):
+    password = next_password(password)
+print(password)