new file mode 100644
--- /dev/null
+++ b/2017/day09/problem
@@ -0,0 +1,119 @@
+--- Day 9: Stream Processing ---
+
+A large stream blocks your path. According to the locals, it's not
+safe to cross the stream at the moment because it's full of garbage.
+You look down at the stream; rather than water, you discover that it's
+a stream of characters.
+
+You sit for a while and record part of the stream (your puzzle input).
+The characters represent groups - sequences that begin with { and end
+with }. Within a group, there are zero or more other things, separated
+by commas: either another group or garbage. Since groups can contain
+other groups, a } only closes the most-recently-opened unclosed group
+- that is, they are nestable. Your puzzle input represents a single,
+large group which itself contains many smaller ones.
+
+Sometimes, instead of a group, you will find garbage. Garbage begins
+with < and ends with >. Between those angle brackets, almost any
+character can appear, including { and }. Within garbage, < has no
+special meaning.
+
+In a futile attempt to clean up the garbage, some program has canceled
+some of the characters within it using !: inside garbage, any
+character that comes after ! should be ignored, including <, >, and
+even another !.
+
+You don't see any characters that deviate from these rules. Outside
+garbage, you only find well-formed groups, and garbage always
+terminates according to the rules above.
+
+Here are some self-contained pieces of garbage:
+
+    <>, empty garbage.
+
+    <random characters>, garbage containing random characters.
+
+    <<<<>, because the extra < are ignored.
+
+    <{!>}>, because the first > is canceled.
+
+    <!!>, because the second ! is canceled, allowing the > to
+    terminate the garbage.
+
+    <!!!>>, because the second ! and the first > are canceled.
+
+    <{o"i!a,<{i<a>, which ends at the first >.
+
+Here are some examples of whole streams and the number of groups they contain:
+
+    {}, 1 group.
+
+    {{{}}}, 3 groups.
+
+    {{},{}}, also 3 groups.
+
+    {{{},{},{{}}}}, 6 groups.
+
+    {<{},{},{{}}>}, 1 group (which itself contains garbage).
+
+    {<a>,<a>,<a>,<a>}, 1 group.
+
+    {{<a>},{<a>},{<a>},{<a>}}, 5 groups.
+
+    {{<!>},{<!>},{<!>},{<a>}}, 2 groups (since all but the last > are
+    canceled).
+
+
+Your goal is to find the total score for all groups in your input.
+Each group is assigned a score which is one more than the score of the
+group that immediately contains it. (The outermost group gets a score
+of 1.)
+
+    {}, score of 1.
+
+    {{{}}}, score of 1 + 2 + 3 = 6.
+
+    {{},{}}, score of 1 + 2 + 2 = 5.
+
+    {{{},{},{{}}}}, score of 1 + 2 + 3 + 3 + 3 + 4 = 16.
+
+    {<a>,<a>,<a>,<a>}, score of 1.
+
+    {{<ab>},{<ab>},{<ab>},{<ab>}}, score of 1 + 2 + 2 + 2 + 2 = 9.
+
+    {{<!!>},{<!!>},{<!!>},{<!!>}}, score of 1 + 2 + 2 + 2 + 2 = 9.
+
+    {{<a!>},{<a!>},{<a!>},{<ab>}}, score of 1 + 2 = 3.
+
+What is the total score for all groups in your input?
+
+Your puzzle answer was 12803.
+
+--- Part Two ---
+
+Now, you're ready to remove the garbage.
+
+To prove you've removed it, you need to count all of the characters
+within the garbage. The leading and trailing < and > don't count, nor
+do any canceled characters or the ! doing the canceling.
+
+    <>, 0 characters.
+
+    <random characters>, 17 characters.
+
+    <<<<>, 3 characters.
+
+    <{!>}>, 2 characters.
+
+    <!!>, 0 characters.
+
+    <!!!>>, 0 characters.
+
+    <{o"i!a,<{i<a>, 10 characters.
+
+How many non-canceled characters are within the garbage in your puzzle
+input?
+
+Your puzzle answer was 6425.
+
+Both parts of this puzzle are complete! They provide two gold stars: **