Hello, Codeforces!

We are going to host a new contest at csacademy.com. Round #69 will take place on Wednesday, February/14/2018 15:05 (UTC). This round will be a Div. 2, affecting users with a rating below **1800**.

#### Facebook event

Recently, Facebook has reintroduced the possibility of recurring events. If you choose "Interested" here, you will be notified before each round we organise from now on.

#### Contest format:

- You will have to solve
**5**tasks in**2**hours. - There will be full feedback throughout the entire contest.
- Tasks will not have partial scoring, so you need to pass all test cases for a solution to count (ACM-ICPC-style).
- Tasks will have dynamic scores. According to the number of users that solve a problem the score will vary between 100 and 1000.
- Besides the score, each user will also get a penalty that is going to be used as a tie breaker.

#### About the penalty system:

- Computed using the following formula: the minute of the last accepted solution + the penalty for each solved task. The penalty for a solved task is equal to log2 (no_of_submissions) * 5.
- Solutions that don't compile or don't pass the example test cases are ignored.
- Once you solve a task you can still resubmit. All the following solutions will be ignored for both the score and the penalty.

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Nice position to be in ;p

Again memes about

`Valentine's Day`

.Thanks, I've been wondering what it could be about.

How to solve E?

I solved it by coding a dp solution and then trying to guess a recurrence relation from the results for smaller values of n. After finding the recurrence relation, then it was a simple matrix exponentiation. I could not solve the problem during the contest as the whole process took me a bit more than 2 hours. Can anyone who solved it during the contest, tell a bit more about how to approach these types of problems? The editorial did not help much here.