## 「CodeForces 1198D」 Rectangle Painting 1

There is a square grid of size $n \times n$. Some cells are colored in black, all others are colored in white. In one operation you can select some rectangle and color all its cells in white. It costs $\max(h, w)$ to color a rectangle of size $h \times w$. You are to make all cells white for minimum total cost.

## 「CodeForces 1247E」Rock Is Push

You are at the top left cell (1,1) of an 𝑛×𝑚 labyrinth. Your goal is to get to the bottom right cell (𝑛,𝑚). You can only move right or down, one cell per step. Moving right from a cell (𝑥,𝑦) takes you to the cell (𝑥,𝑦+1), while moving down takes you to the cell (𝑥+1,𝑦).

## 「Comet OJ - Contest #11」usiness

「只是我今天的 $\alphaα$ 设得比较大…」替罪羊树辩解的同时，心虚地偏了下身子试图遮住背后长歪二叉树的虚影。

## 「POJ 1417」True Liars

After having drifted about in a small boat for a couple of days, Akira Crusoe Maeda was finally cast ashore on a foggy island. Though he was exhausted and despaired, he was still fortunate to remember a legend of the foggy island, which he had heard from patriarchs in his childhood. This must be the island in the legend. In the legend, two tribes have inhabited the island, one is divine and the other is devilish, once members of the divine tribe bless you, your future is bright and promising, and your soul will eventually go to Heaven, in contrast, once members of the devilish tribe curse you, your future is bleak and hopeless, and your soul will eventually fall down to Hell.

## 「CF1012C」 Hills

Welcome to Innopolis city. Throughout the whole year, Innopolis citizens suffer from everlasting city construction.

From the window in your room, you see the sequence of n hills, where i-th of them has height ai. The Innopolis administration wants to build some houses on the hills. However, for the sake of city appearance, a house can be only built on the hill, which is strictly higher than neighbouring hills (if they are present). For example, if the sequence of heights is 5, 4, 6, 2, then houses could be built on hills with heights 5 and 6 only.

## 「CF 1152D」 Neko and Aki's Prank

Neko is playing with his toys on the backyard of Aki's house. Aki decided to play a prank on him, by secretly putting catnip into Neko's toys. Unfortunately, he went overboard and put an entire bag of catnip into the toys...

It took Neko an entire day to turn back to normal. Neko reported to Aki that he saw a lot of weird things, including a trie of all correct bracket sequences of length 2n.