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Consider some set of distinct characters $$$A$$$ and some string $$$S$$$, consisting of exactly $$$n$$$ characters, where each character is present in $$$A$$$.You are given an array of $$$m$$$ integers $$$b$$$ ($$$b_1 < b_2 < \dots < b_m$$$). You are allowed to perform the following move on the string $$$S$$$: Choose some valid $$$i$$$ and set $$$k = b_i$$$; Take the first $$$k$$$ characters of $$$S = Pr_k$$$; Take the last $$$k$$$ characters of $$$S = Su_k$$$; Substitute the first $$$k$$$ characters of $$$S$$$ with the reversed $$$Su_k$$$; Substitute the last $$$k$$$ characters of $$$S$$$ with the reversed $$$Pr_k$$$. For example, let's take a look at $$$S =$$$ "abcdefghi" and $$$k = 2$$$. $$$Pr_2 =$$$ "ab", $$$Su_2 =$$$ "hi". Reversed $$$Pr_2 =$$$ "ba", $$$Su_2 =$$$ "ih". Thus, the resulting $$$S$$$ is "ihcdefgba".The move can be performed arbitrary number of times (possibly zero). Any $$$i$$$ can be selected multiple times over these moves.Let's call some strings $$$S$$$ and $$$T$$$ equal if and only if there exists such a sequence of moves to transmute string $$$S$$$ to string $$$T$$$. For the above example strings "abcdefghi" and "ihcdefgba" are equal. Also note that this implies $$$S = S$$$.The task is simple. Count the number of distinct strings.The answer can be huge enough, so calculate it modulo $$$998244353$$$. | ['strings'] |
This is the hard version of the problem. The difference is the constraint on the sum of lengths of strings and the number of test cases. You can make hacks only if you solve all versions of this task.You are given a string $$$s$$$, consisting of lowercase English letters. Find the longest string, $$$t$$$, which satisfies the following conditions: The length of $$$t$$$ does not exceed the length of $$$s$$$. $$$t$$$ is a palindrome. There exists two strings $$$a$$$ and $$$b$$$ (possibly empty), such that $$$t = a + b$$$ ( "$$$+$$$" represents concatenation), and $$$a$$$ is prefix of $$$s$$$ while $$$b$$$ is suffix of $$$s$$$. | ['strings'] |
You are a rebel leader and you are planning to start a revolution in your country. But the evil Government found out about your plans and set your punishment in the form of correctional labor.You must paint a fence which consists of $$$10^{100}$$$ planks in two colors in the following way (suppose planks are numbered from left to right from $$$0$$$): if the index of the plank is divisible by $$$r$$$ (such planks have indices $$$0$$$, $$$r$$$, $$$2r$$$ and so on) then you must paint it red; if the index of the plank is divisible by $$$b$$$ (such planks have indices $$$0$$$, $$$b$$$, $$$2b$$$ and so on) then you must paint it blue; if the index is divisible both by $$$r$$$ and $$$b$$$ you can choose the color to paint the plank; otherwise, you don't need to paint the plank at all (and it is forbidden to spent paint on it). Furthermore, the Government added one additional restriction to make your punishment worse. Let's list all painted planks of the fence in ascending order: if there are $$$k$$$ consecutive planks with the same color in this list, then the Government will state that you failed the labor and execute you immediately. If you don't paint the fence according to the four aforementioned conditions, you will also be executed.The question is: will you be able to accomplish the labor (the time is not important) or the execution is unavoidable and you need to escape at all costs. | ['math', 'number theory'] |
Today, Wet Shark is given n bishops on a 1000 by 1000 grid. Both rows and columns of the grid are numbered from 1 to 1000. Rows are numbered from top to bottom, while columns are numbered from left to right.Wet Shark thinks that two bishops attack each other if they share the same diagonal. Note, that this is the only criteria, so two bishops may attack each other (according to Wet Shark) even if there is another bishop located between them. Now Wet Shark wants to count the number of pairs of bishops that attack each other. | [] |
Galya is playing one-dimensional Sea Battle on a 1 × n grid. In this game a ships are placed on the grid. Each of the ships consists of b consecutive cells. No cell can be part of two ships, however, the ships can touch each other.Galya doesn't know the ships location. She can shoot to some cells and after each shot she is told if that cell was a part of some ship (this case is called "hit") or not (this case is called "miss").Galya has already made k shots, all of them were misses.Your task is to calculate the minimum number of cells such that if Galya shoot at all of them, she would hit at least one ship.It is guaranteed that there is at least one valid ships placement. | ['math'] |
You are given two arrays A and B, each of size n. The error, E, between these two arrays is defined . You have to perform exactly k1 operations on array A and exactly k2 operations on array B. In one operation, you have to choose one element of the array and increase or decrease it by 1.Output the minimum possible value of error after k1 operations on array A and k2 operations on array B have been performed. | [] |
Egor wants to achieve a rating of 1600 points on the well-known chess portal ChessForces and he needs your help!Before you start solving the problem, Egor wants to remind you how the chess pieces move. Chess rook moves along straight lines up and down, left and right, as many squares as it wants. And when it wants, it can stop. The queen walks in all directions vertically and diagonally at any distance. You can see the examples below. To reach the goal, Egor should research the next topic:There is an $$$N \times N$$$ board. Each cell of the board has a number from $$$1$$$ to $$$N ^ 2$$$ in it and numbers in all cells are distinct.In the beginning, some chess figure stands in the cell with the number $$$1$$$. Note that this cell is already considered as visited. After that every move is determined by the following rules: Among all not visited yet cells to which the figure can get in one move, it goes to the cell that has minimal number. If all accessible cells were already visited and some cells are not yet visited, then the figure is teleported to the not visited cell that has minimal number. If this step happens, the piece pays a fee of $$$1$$$ vun. If all cells are already visited, the process is stopped. Egor should find an $$$N \times N$$$ board on which the rook pays strictly less vuns than the queen during the round with this numbering. Help him to find such $$$N \times N$$$ numbered board, or tell that it doesn't exist. | [] |
In Fire City, there are $$$n$$$ intersections and $$$m$$$ one-way roads. The $$$i$$$-th road goes from intersection $$$a_i$$$ to $$$b_i$$$ and has length $$$l_i$$$ miles. There are $$$q$$$ cars that may only drive along those roads. The $$$i$$$-th car starts at intersection $$$v_i$$$ and has an odometer that begins at $$$s_i$$$, increments for each mile driven, and resets to $$$0$$$ whenever it reaches $$$t_i$$$. Phoenix has been tasked to drive cars along some roads (possibly none) and return them to their initial intersection with the odometer showing $$$0$$$.For each car, please find if this is possible. A car may visit the same road or intersection an arbitrary number of times. The odometers don't stop counting the distance after resetting, so odometers may also be reset an arbitrary number of times. | ['math', 'graphs', 'number theory'] |
Nikephoros and Polycarpus play rock-paper-scissors. The loser gets pinched (not too severely!).Let us remind you the rules of this game. Rock-paper-scissors is played by two players. In each round the players choose one of three items independently from each other. They show the items with their hands: a rock, scissors or paper. The winner is determined by the following rules: the rock beats the scissors, the scissors beat the paper and the paper beats the rock. If the players choose the same item, the round finishes with a draw.Nikephoros and Polycarpus have played n rounds. In each round the winner gave the loser a friendly pinch and the loser ended up with a fresh and new red spot on his body. If the round finished in a draw, the players did nothing and just played on.Nikephoros turned out to have worked out the following strategy: before the game began, he chose some sequence of items A = (a1, a2, ..., am), and then he cyclically showed the items from this sequence, starting from the first one. Cyclically means that Nikephoros shows signs in the following order: a1, a2, ..., am, a1, a2, ..., am, a1, ... and so on. Polycarpus had a similar strategy, only he had his own sequence of items B = (b1, b2, ..., bk).Determine the number of red spots on both players after they've played n rounds of the game. You can consider that when the game began, the boys had no red spots on them. | ['math'] |
There are $$$n$$$ students at your university. The programming skill of the $$$i$$$-th student is $$$a_i$$$. As a coach, you want to divide them into teams to prepare them for the upcoming ICPC finals. Just imagine how good this university is if it has $$$2 \cdot 10^5$$$ students ready for the finals!Each team should consist of at least three students. Each student should belong to exactly one team. The diversity of a team is the difference between the maximum programming skill of some student that belongs to this team and the minimum programming skill of some student that belongs to this team (in other words, if the team consists of $$$k$$$ students with programming skills $$$a[i_1], a[i_2], \dots, a[i_k]$$$, then the diversity of this team is $$$\max\limits_{j=1}^{k} a[i_j] - \min\limits_{j=1}^{k} a[i_j]$$$).The total diversity is the sum of diversities of all teams formed.Your task is to minimize the total diversity of the division of students and find the optimal way to divide the students. | [] |
Sherlock Holmes found a mysterious correspondence of two VIPs and made up his mind to read it. But there is a problem! The correspondence turned out to be encrypted. The detective tried really hard to decipher the correspondence, but he couldn't understand anything. At last, after some thought, he thought of something. Let's say there is a word s, consisting of |s| lowercase Latin letters. Then for one operation you can choose a certain position p (1 ≤ p < |s|) and perform one of the following actions: either replace letter sp with the one that alphabetically follows it and replace letter sp + 1 with the one that alphabetically precedes it; or replace letter sp with the one that alphabetically precedes it and replace letter sp + 1 with the one that alphabetically follows it. Let us note that letter "z" doesn't have a defined following letter and letter "a" doesn't have a defined preceding letter. That's why the corresponding changes are not acceptable. If the operation requires performing at least one unacceptable change, then such operation cannot be performed.Two words coincide in their meaning iff one of them can be transformed into the other one as a result of zero or more operations.Sherlock Holmes needs to learn to quickly determine the following for each word: how many words can exist that coincide in their meaning with the given word, but differs from the given word in at least one character? Count this number for him modulo 1000000007 (109 + 7). | [] |
Vasya plays one very well-known and extremely popular MMORPG game. His game character has k skill; currently the i-th of them equals to ai. Also this game has a common rating table in which the participants are ranked according to the product of all the skills of a hero in the descending order.Vasya decided to 'upgrade' his character via the game store. This store offers n possible ways to improve the hero's skills; Each of these ways belongs to one of three types: assign the i-th skill to b; add b to the i-th skill; multiply the i-th skill by b. Unfortunately, a) every improvement can only be used once; b) the money on Vasya's card is enough only to purchase not more than m of the n improvements. Help Vasya to reach the highest ranking in the game. To do this tell Vasya which of improvements he has to purchase and in what order he should use them to make his rating become as high as possible. If there are several ways to achieve it, print any of them. | [] |
This is the second subtask of problem F. The only differences between this and the first subtask are the constraints on the value of $$$m$$$ and the time limit. It is sufficient to solve this subtask in order to hack it, but you need to solve both subtasks in order to hack the first one.There are $$$n+1$$$ distinct colours in the universe, numbered $$$0$$$ through $$$n$$$. There is a strip of paper $$$m$$$ centimetres long initially painted with colour $$$0$$$. Alice took a brush and painted the strip using the following process. For each $$$i$$$ from $$$1$$$ to $$$n$$$, in this order, she picks two integers $$$0 \leq a_i < b_i \leq m$$$, such that the segment $$$[a_i, b_i]$$$ is currently painted with a single colour, and repaints it with colour $$$i$$$. Alice chose the segments in such a way that each centimetre is now painted in some colour other than $$$0$$$. Formally, the segment $$$[i-1, i]$$$ is painted with colour $$$c_i$$$ ($$$c_i \neq 0$$$). Every colour other than $$$0$$$ is visible on the strip.Count the number of different pairs of sequences $$$\{a_i\}_{i=1}^n$$$, $$$\{b_i\}_{i=1}^n$$$ that result in this configuration. Since this number may be large, output it modulo $$$998244353$$$. | [] |
There are $$$n$$$ seats in the train's car and there is exactly one passenger occupying every seat. The seats are numbered from $$$1$$$ to $$$n$$$ from left to right. The trip is long, so each passenger will become hungry at some moment of time and will go to take boiled water for his noodles. The person at seat $$$i$$$ ($$$1 \leq i \leq n$$$) will decide to go for boiled water at minute $$$t_i$$$.Tank with a boiled water is located to the left of the $$$1$$$-st seat. In case too many passengers will go for boiled water simultaneously, they will form a queue, since there can be only one passenger using the tank at each particular moment of time. Each passenger uses the tank for exactly $$$p$$$ minutes. We assume that the time it takes passengers to go from their seat to the tank is negligibly small. Nobody likes to stand in a queue. So when the passenger occupying the $$$i$$$-th seat wants to go for a boiled water, he will first take a look on all seats from $$$1$$$ to $$$i - 1$$$. In case at least one of those seats is empty, he assumes that those people are standing in a queue right now, so he would be better seating for the time being. However, at the very first moment he observes that all seats with numbers smaller than $$$i$$$ are busy, he will go to the tank.There is an unspoken rule, that in case at some moment several people can go to the tank, than only the leftmost of them (that is, seating on the seat with smallest number) will go to the tank, while all others will wait for the next moment.Your goal is to find for each passenger, when he will receive the boiled water for his noodles. | [] |
You are given two integers $$$n$$$ and $$$m$$$ ($$$m < n$$$). Consider a convex regular polygon of $$$n$$$ vertices. Recall that a regular polygon is a polygon that is equiangular (all angles are equal in measure) and equilateral (all sides have the same length). Examples of convex regular polygons Your task is to say if it is possible to build another convex regular polygon with $$$m$$$ vertices such that its center coincides with the center of the initial polygon and each of its vertices is some vertex of the initial polygon.You have to answer $$$t$$$ independent test cases. | ['math', 'number theory', 'geometry'] |
This is an interactive problem.You're given a tree consisting of $$$n$$$ nodes, rooted at node $$$1$$$. A tree is a connected graph with no cycles.We chose a hidden node $$$x$$$. In order to find this node, you can ask queries of two types: d $$$u$$$ ($$$1 \le u \le n$$$). We will answer with the distance between nodes $$$u$$$ and $$$x$$$. The distance between two nodes is the number of edges in the shortest path between them. s $$$u$$$ ($$$1 \le u \le n$$$). We will answer with the second node on the path from $$$u$$$ to $$$x$$$. However, there's a plot twist. If $$$u$$$ is not an ancestor of $$$x$$$, you'll receive "Wrong answer" verdict! Node $$$a$$$ is called an ancestor of node $$$b$$$ if $$$a \ne b$$$ and the shortest path from node $$$1$$$ to node $$$b$$$ passes through node $$$a$$$. Note that in this problem a node is not an ancestor of itself.Can you find $$$x$$$ in no more than $$$36$$$ queries? The hidden node is fixed in each test beforehand and does not depend on your queries. | ['graphs', 'trees'] |
You are given an array $$$a$$$ of length $$$n$$$, and an integer $$$x$$$. You can perform the following operation as many times as you would like (possibly zero): replace two adjacent elements of the array by their sum. For example, if the initial array was $$$[3, 6, 9]$$$, in a single operation one can replace the last two elements by their sum, yielding an array $$$[3, 15]$$$, or replace the first two elements to get an array $$$[9, 9]$$$. Note that the size of the array decreases after each operation.The beauty of an array $$$b=[b_1, \ldots, b_k]$$$ is defined as $$$\sum_{i=1}^k \left\lceil \frac{b_i}{x} \right\rceil$$$, which means that we divide each element by $$$x$$$, round it up to the nearest integer, and sum up the resulting values. For example, if $$$x = 3$$$, and the array is $$$[4, 11, 6]$$$, the beauty of the array is equal to $$$\left\lceil \frac{4}{3} \right\rceil + \left\lceil \frac{11}{3} \right\rceil + \left\lceil \frac{6}{3} \right\rceil = 2 + 4 + 2 = 8$$$.Please determine the minimum and the maximum beauty you can get by performing some operations on the original array. | ['math', 'number theory'] |
Recently in Divanovo, a huge river locks system was built. There are now $$$n$$$ locks, the $$$i$$$-th of them has the volume of $$$v_i$$$ liters, so that it can contain any amount of water between $$$0$$$ and $$$v_i$$$ liters. Each lock has a pipe attached to it. When the pipe is open, $$$1$$$ liter of water enters the lock every second.The locks system is built in a way to immediately transfer all water exceeding the volume of the lock $$$i$$$ to the lock $$$i + 1$$$. If the lock $$$i + 1$$$ is also full, water will be transferred further. Water exceeding the volume of the last lock pours out to the river. The picture illustrates $$$5$$$ locks with two open pipes at locks $$$1$$$ and $$$3$$$. Because locks $$$1$$$, $$$3$$$, and $$$4$$$ are already filled, effectively the water goes to locks $$$2$$$ and $$$5$$$. Note that the volume of the $$$i$$$-th lock may be greater than the volume of the $$$i + 1$$$-th lock.To make all locks work, you need to completely fill each one of them. The mayor of Divanovo is interested in $$$q$$$ independent queries. For each query, suppose that initially all locks are empty and all pipes are closed. Then, some pipes are opened simultaneously. For the $$$j$$$-th query the mayor asks you to calculate the minimum number of pipes to open so that all locks are filled no later than after $$$t_j$$$ seconds.Please help the mayor to solve this tricky problem and answer his queries. | ['math'] |
On a number line there are n balls. At time moment 0 for each ball the following data is known: its coordinate xi, speed vi (possibly, negative) and weight mi. The radius of the balls can be ignored.The balls collide elastically, i.e. if two balls weighing m1 and m2 and with speeds v1 and v2 collide, their new speeds will be: .Your task is to find out, where each ball will be t seconds after. | ['math'] |
You are given a string s, consisting of small Latin letters. Let's denote the length of the string as |s|. The characters in the string are numbered starting from 1. Your task is to find out if it is possible to rearrange characters in string s so that for any prime number p ≤ |s| and for any integer i ranging from 1 to |s| / p (inclusive) the following condition was fulfilled sp = sp × i. If the answer is positive, find one way to rearrange the characters. | ['strings', 'number theory'] |
You are given two integers $$$A$$$ and $$$B$$$, calculate the number of pairs $$$(a, b)$$$ such that $$$1 \le a \le A$$$, $$$1 \le b \le B$$$, and the equation $$$a \cdot b + a + b = conc(a, b)$$$ is true; $$$conc(a, b)$$$ is the concatenation of $$$a$$$ and $$$b$$$ (for example, $$$conc(12, 23) = 1223$$$, $$$conc(100, 11) = 10011$$$). $$$a$$$ and $$$b$$$ should not contain leading zeroes. | ['math'] |
Phoenix has decided to become a scientist! He is currently investigating the growth of bacteria.Initially, on day $$$1$$$, there is one bacterium with mass $$$1$$$.Every day, some number of bacteria will split (possibly zero or all). When a bacterium of mass $$$m$$$ splits, it becomes two bacteria of mass $$$\frac{m}{2}$$$ each. For example, a bacterium of mass $$$3$$$ can split into two bacteria of mass $$$1.5$$$.Also, every night, the mass of every bacteria will increase by one.Phoenix is wondering if it is possible for the total mass of all the bacteria to be exactly $$$n$$$. If it is possible, he is interested in the way to obtain that mass using the minimum possible number of nights. Help him become the best scientist! | ['math'] |
An integer array $$$a_1, a_2, \ldots, a_n$$$ is being transformed into an array of lowercase English letters using the following prodecure:While there is at least one number in the array: Choose any number $$$x$$$ from the array $$$a$$$, and any letter of the English alphabet $$$y$$$. Replace all occurrences of number $$$x$$$ with the letter $$$y$$$. For example, if we initially had an array $$$a = [2, 3, 2, 4, 1]$$$, then we could transform it the following way: Choose the number $$$2$$$ and the letter c. After that $$$a = [c, 3, c, 4, 1]$$$. Choose the number $$$3$$$ and the letter a. After that $$$a = [c, a, c, 4, 1]$$$. Choose the number $$$4$$$ and the letter t. After that $$$a = [c, a, c, t, 1]$$$. Choose the number $$$1$$$ and the letter a. After that $$$a = [c, a, c, t, a]$$$. After the transformation all letters are united into a string, in our example we get the string "cacta".Having the array $$$a$$$ and the string $$$s$$$ determine if the string $$$s$$$ could be got from the array $$$a$$$ after the described transformation? | [] |
After the lessons n groups of schoolchildren went outside and decided to visit Polycarpus to celebrate his birthday. We know that the i-th group consists of si friends (1 ≤ si ≤ 4), and they want to go to Polycarpus together. They decided to get there by taxi. Each car can carry at most four passengers. What minimum number of cars will the children need if all members of each group should ride in the same taxi (but one taxi can take more than one group)? | [] |
Polycarp found on the street an array $$$a$$$ of $$$n$$$ elements.Polycarp invented his criterion for the beauty of an array. He calls an array $$$a$$$ beautiful if at least one of the following conditions must be met for each different pair of indices $$$i \ne j$$$: $$$a_i$$$ is divisible by $$$a_j$$$; or $$$a_j$$$ is divisible by $$$a_i$$$. For example, if: $$$n=5$$$ and $$$a=[7, 9, 3, 14, 63]$$$, then the $$$a$$$ array is not beautiful (for $$$i=4$$$ and $$$j=2$$$, none of the conditions above is met); $$$n=3$$$ and $$$a=[2, 14, 42]$$$, then the $$$a$$$ array is beautiful; $$$n=4$$$ and $$$a=[45, 9, 3, 18]$$$, then the $$$a$$$ array is not beautiful (for $$$i=1$$$ and $$$j=4$$$ none of the conditions above is met); Ugly arrays upset Polycarp, so he wants to remove some elements from the array $$$a$$$ so that it becomes beautiful. Help Polycarp determine the smallest number of elements to remove to make the array $$$a$$$ beautiful. | ['math', 'number theory'] |
Vasya plays FreeDiv. In this game he manages a huge state, which has n cities and m two-way roads between them. Unfortunately, not from every city you can reach any other one moving along these roads. Therefore Vasya decided to divide the state into provinces so that in every province, one could reach from every city all the cities of the province, but there are no roads between provinces. Unlike other turn-based strategies, in FreeDiv a player has the opportunity to build tunnels between cities. The tunnels are two-way roads along which one can move armies undetected by the enemy. However, no more than one tunnel can be connected to each city. As for Vasya, he wants to build a network of tunnels so that any pair of cities in his state were reachable by some path consisting of roads and a tunnels. But at that no more than k tunnels are connected to each province (otherwise, the province will be difficult to keep in case other provinces are captured by enemy armies).Vasya discovered that maybe he will not be able to build such a network for the current condition of the state. Maybe he'll have first to build several roads between cities in different provinces to merge the provinces. Your task is to determine the minimum number of roads Vasya needs to build so that it was possible to build the required network of tunnels in the resulting state. | ['graphs'] |
Mr. Kitayuta has just bought an undirected graph consisting of n vertices and m edges. The vertices of the graph are numbered from 1 to n. Each edge, namely edge i, has a color ci, connecting vertex ai and bi.Mr. Kitayuta wants you to process the following q queries.In the i-th query, he gives you two integers — ui and vi.Find the number of the colors that satisfy the following condition: the edges of that color connect vertex ui and vertex vi directly or indirectly. | ['graphs'] |
Polycarpus has a hobby — he develops an unusual social network. His work is almost completed, and there is only one more module to implement — the module which determines friends. Oh yes, in this social network one won't have to add friends manually! Pairs of friends are deduced in the following way. Let's assume that user A sent user B a message at time t1, and user B sent user A a message at time t2. If 0 < t2 - t1 ≤ d, then user B's message was an answer to user A's one. Users A and B are considered to be friends if A answered at least one B's message or B answered at least one A's message.You are given the log of messages in chronological order and a number d. Find all pairs of users who will be considered to be friends. | [] |
You are given a directed graph of $$$n$$$ vertices and $$$m$$$ edges. Vertices are numbered from $$$1$$$ to $$$n$$$. There is a token in vertex $$$1$$$.The following actions are allowed: Token movement. To move the token from vertex $$$u$$$ to vertex $$$v$$$ if there is an edge $$$u \to v$$$ in the graph. This action takes $$$1$$$ second. Graph transposition. To transpose all the edges in the graph: replace each edge $$$u \to v$$$ by an edge $$$v \to u$$$. This action takes increasingly more time: $$$k$$$-th transposition takes $$$2^{k-1}$$$ seconds, i.e. the first transposition takes $$$1$$$ second, the second one takes $$$2$$$ seconds, the third one takes $$$4$$$ seconds, and so on. The goal is to move the token from vertex $$$1$$$ to vertex $$$n$$$ in the shortest possible time. Print this time modulo $$$998\,244\,353$$$. | ['graphs'] |
You are given a matrix $$$a$$$ of size $$$n \times m$$$ consisting of integers.You can choose no more than $$$\left\lfloor\frac{m}{2}\right\rfloor$$$ elements in each row. Your task is to choose these elements in such a way that their sum is divisible by $$$k$$$ and this sum is the maximum.In other words, you can choose no more than a half (rounded down) of elements in each row, you have to find the maximum sum of these elements divisible by $$$k$$$.Note that you can choose zero elements (and the sum of such set is $$$0$$$). | [] |
Limak is a little polar bear. He doesn't have many toys and thus he often plays with polynomials.He considers a polynomial valid if its degree is n and its coefficients are integers not exceeding k by the absolute value. More formally:Let a0, a1, ..., an denote the coefficients, so . Then, a polynomial P(x) is valid if all the following conditions are satisfied: ai is integer for every i; |ai| ≤ k for every i; an ≠ 0. Limak has recently got a valid polynomial P with coefficients a0, a1, a2, ..., an. He noticed that P(2) ≠ 0 and he wants to change it. He is going to change one coefficient to get a valid polynomial Q of degree n that Q(2) = 0. Count the number of ways to do so. You should count two ways as a distinct if coefficients of target polynoms differ. | ['math'] |
A string is called a k-string if it can be represented as k concatenated copies of some string. For example, the string "aabaabaabaab" is at the same time a 1-string, a 2-string and a 4-string, but it is not a 3-string, a 5-string, or a 6-string and so on. Obviously any string is a 1-string.You are given a string s, consisting of lowercase English letters and a positive integer k. Your task is to reorder the letters in the string s in such a way that the resulting string is a k-string. | ['strings'] |
There is an undirected, connected graph with $$$n$$$ vertices and $$$m$$$ weighted edges. A walk from vertex $$$u$$$ to vertex $$$v$$$ is defined as a sequence of vertices $$$p_1,p_2,\ldots,p_k$$$ (which are not necessarily distinct) starting with $$$u$$$ and ending with $$$v$$$, such that $$$p_i$$$ and $$$p_{i+1}$$$ are connected by an edge for $$$1 \leq i < k$$$.We define the length of a walk as follows: take the ordered sequence of edges and write down the weights on each of them in an array. Now, write down the bitwise AND of every nonempty prefix of this array. The length of the walk is the MEX of all these values.More formally, let us have $$$[w_1,w_2,\ldots,w_{k-1}]$$$ where $$$w_i$$$ is the weight of the edge between $$$p_i$$$ and $$$p_{i+1}$$$. Then the length of the walk is given by $$$\mathrm{MEX}(\{w_1,\,w_1\& w_2,\,\ldots,\,w_1\& w_2\& \ldots\& w_{k-1}\})$$$, where $$$\&$$$ denotes the bitwise AND operation.Now you must process $$$q$$$ queries of the form u v. For each query, find the minimum possible length of a walk from $$$u$$$ to $$$v$$$.The MEX (minimum excluded) of a set is the smallest non-negative integer that does not belong to the set. For instance: The MEX of $$$\{2,1\}$$$ is $$$0$$$, because $$$0$$$ does not belong to the set. The MEX of $$$\{3,1,0\}$$$ is $$$2$$$, because $$$0$$$ and $$$1$$$ belong to the set, but $$$2$$$ does not. The MEX of $$$\{0,3,1,2\}$$$ is $$$4$$$ because $$$0$$$, $$$1$$$, $$$2$$$ and $$$3$$$ belong to the set, but $$$4$$$ does not. | ['graphs'] |
You are given a set Y of n distinct positive integers y1, y2, ..., yn.Set X of n distinct positive integers x1, x2, ..., xn is said to generate set Y if one can transform X to Y by applying some number of the following two operation to integers in X: Take any integer xi and multiply it by two, i.e. replace xi with 2·xi. Take any integer xi, multiply it by two and add one, i.e. replace xi with 2·xi + 1. Note that integers in X are not required to be distinct after each operation.Two sets of distinct integers X and Y are equal if they are equal as sets. In other words, if we write elements of the sets in the array in the increasing order, these arrays would be equal.Note, that any set of integers (or its permutation) generates itself.You are given a set Y and have to find a set X that generates Y and the maximum element of X is mininum possible. | ['strings', 'trees'] |
You are given a string $$$s$$$ consisting of lowercase letters of the English alphabet. You must perform the following algorithm on $$$s$$$: Let $$$x$$$ be the length of the longest prefix of $$$s$$$ which occurs somewhere else in $$$s$$$ as a contiguous substring (the other occurrence may also intersect the prefix). If $$$x = 0$$$, break. Otherwise, remove the first $$$x$$$ characters of $$$s$$$, and repeat. A prefix is a string consisting of several first letters of a given string, without any reorders. An empty prefix is also a valid prefix. For example, the string "abcd" has 5 prefixes: empty string, "a", "ab", "abc" and "abcd".For instance, if we perform the algorithm on $$$s =$$$ "abcabdc", Initially, "ab" is the longest prefix that also appears somewhere else as a substring in $$$s$$$, so $$$s =$$$ "cabdc" after $$$1$$$ operation. Then, "c" is the longest prefix that also appears somewhere else as a substring in $$$s$$$, so $$$s =$$$ "abdc" after $$$2$$$ operations. Now $$$x=0$$$ (because there are no non-empty prefixes of "abdc" that also appear somewhere else as a substring in $$$s$$$), so the algorithm terminates. Find the final state of the string after performing the algorithm. | ['strings'] |
Little Masha loves arranging her toys into piles on the floor. And she also hates it when somebody touches her toys. One day Masha arranged all her n toys into several piles and then her elder brother Sasha came and gathered all the piles into one. Having seen it, Masha got very upset and started crying. Sasha still can't calm Masha down and mom is going to come home soon and punish Sasha for having made Masha crying. That's why he decides to restore the piles' arrangement. However, he doesn't remember at all the way the toys used to lie. Of course, Masha remembers it, but she can't talk yet and can only help Sasha by shouting happily when he arranges the toys in the way they used to lie. That means that Sasha will have to arrange the toys in every possible way until Masha recognizes the needed arrangement. The relative position of the piles and toys in every pile is irrelevant, that's why the two ways of arranging the toys are considered different if can be found two such toys that when arranged in the first way lie in one and the same pile and do not if arranged in the second way. Sasha is looking for the fastest way of trying all the ways because mom will come soon. With every action Sasha can take a toy from any pile and move it to any other pile (as a result a new pile may appear or the old one may disappear). Sasha wants to find the sequence of actions as a result of which all the pile arrangement variants will be tried exactly one time each. Help Sasha. As we remember, initially all the toys are located in one pile. | [] |
Ivan has an array consisting of n different integers. He decided to reorder all elements in increasing order. Ivan loves merge sort so he decided to represent his array with one or several increasing sequences which he then plans to merge into one sorted array.Ivan represent his array with increasing sequences with help of the following algorithm.While there is at least one unused number in array Ivan repeats the following procedure: iterate through array from the left to the right; Ivan only looks at unused numbers on current iteration; if current number is the first unused number on this iteration or this number is greater than previous unused number on current iteration, then Ivan marks the number as used and writes it down. For example, if Ivan's array looks like [1, 3, 2, 5, 4] then he will perform two iterations. On first iteration Ivan will use and write numbers [1, 3, 5], and on second one — [2, 4].Write a program which helps Ivan and finds representation of the given array with one or several increasing sequences in accordance with algorithm described above. | [] |
Let us define a magic grid to be a square matrix of integers of size $$$n \times n$$$, satisfying the following conditions. All integers from $$$0$$$ to $$$(n^2 - 1)$$$ inclusive appear in the matrix exactly once. Bitwise XOR of all elements in a row or a column must be the same for each row and column. You are given an integer $$$n$$$ which is a multiple of $$$4$$$. Construct a magic grid of size $$$n \times n$$$. | [] |
The busses in Berland are equipped with a video surveillance system. The system records information about changes in the number of passengers in a bus after stops.If $$$x$$$ is the number of passengers in a bus just before the current bus stop and $$$y$$$ is the number of passengers in the bus just after current bus stop, the system records the number $$$y-x$$$. So the system records show how number of passengers changed.The test run was made for single bus and $$$n$$$ bus stops. Thus, the system recorded the sequence of integers $$$a_1, a_2, \dots, a_n$$$ (exactly one number for each bus stop), where $$$a_i$$$ is the record for the bus stop $$$i$$$. The bus stops are numbered from $$$1$$$ to $$$n$$$ in chronological order.Determine the number of possible ways how many people could be in the bus before the first bus stop, if the bus has a capacity equals to $$$w$$$ (that is, at any time in the bus there should be from $$$0$$$ to $$$w$$$ passengers inclusive). | ['math'] |
One day Vitaly was going home late at night and wondering: how many people aren't sleeping at that moment? To estimate, Vitaly decided to look which windows are lit in the house he was passing by at that moment.Vitaly sees a building of n floors and 2·m windows on each floor. On each floor there are m flats numbered from 1 to m, and two consecutive windows correspond to each flat. If we number the windows from 1 to 2·m from left to right, then the j-th flat of the i-th floor has windows 2·j - 1 and 2·j in the corresponding row of windows (as usual, floors are enumerated from the bottom). Vitaly thinks that people in the flat aren't sleeping at that moment if at least one of the windows corresponding to this flat has lights on.Given the information about the windows of the given house, your task is to calculate the number of flats where, according to Vitaly, people aren't sleeping. | [] |
In some social network, there are $$$n$$$ users communicating with each other in $$$m$$$ groups of friends. Let's analyze the process of distributing some news between users.Initially, some user $$$x$$$ receives the news from some source. Then he or she sends the news to his or her friends (two users are friends if there is at least one group such that both of them belong to this group). Friends continue sending the news to their friends, and so on. The process ends when there is no pair of friends such that one of them knows the news, and another one doesn't know.For each user $$$x$$$ you have to determine what is the number of users that will know the news if initially only user $$$x$$$ starts distributing it. | ['graphs'] |
Oleg the bank client checks share prices every day. There are n share prices he is interested in. Today he observed that each second exactly one of these prices decreases by k rubles (note that each second exactly one price changes, but at different seconds different prices can change). Prices can become negative. Oleg found this process interesting, and he asked Igor the financial analyst, what is the minimum time needed for all n prices to become equal, or it is impossible at all? Igor is busy right now, so he asked you to help Oleg. Can you answer this question? | ['math'] |
Recently Luba bought a monitor. Monitor is a rectangular matrix of size n × m. But then she started to notice that some pixels cease to work properly. Luba thinks that the monitor will become broken the first moment when it contains a square k × k consisting entirely of broken pixels. She knows that q pixels are already broken, and for each of them she knows the moment when it stopped working. Help Luba to determine when the monitor became broken (or tell that it's still not broken even after all q pixels stopped working). | [] |
You have $$$n$$$ gifts and you want to give all of them to children. Of course, you don't want to offend anyone, so all gifts should be equal between each other. The $$$i$$$-th gift consists of $$$a_i$$$ candies and $$$b_i$$$ oranges.During one move, you can choose some gift $$$1 \le i \le n$$$ and do one of the following operations: eat exactly one candy from this gift (decrease $$$a_i$$$ by one); eat exactly one orange from this gift (decrease $$$b_i$$$ by one); eat exactly one candy and exactly one orange from this gift (decrease both $$$a_i$$$ and $$$b_i$$$ by one). Of course, you can not eat a candy or orange if it's not present in the gift (so neither $$$a_i$$$ nor $$$b_i$$$ can become less than zero).As said above, all gifts should be equal. This means that after some sequence of moves the following two conditions should be satisfied: $$$a_1 = a_2 = \dots = a_n$$$ and $$$b_1 = b_2 = \dots = b_n$$$ (and $$$a_i$$$ equals $$$b_i$$$ is not necessary).Your task is to find the minimum number of moves required to equalize all the given gifts.You have to answer $$$t$$$ independent test cases. | [] |
You've been in love with Coronavirus-chan for a long time, but you didn't know where she lived until now. And just now you found out that she lives in a faraway place called Naha. You immediately decided to take a vacation and visit Coronavirus-chan. Your vacation lasts exactly $$$x$$$ days and that's the exact number of days you will spend visiting your friend. You will spend exactly $$$x$$$ consecutive (successive) days visiting Coronavirus-chan.They use a very unusual calendar in Naha: there are $$$n$$$ months in a year, $$$i$$$-th month lasts exactly $$$d_i$$$ days. Days in the $$$i$$$-th month are numbered from $$$1$$$ to $$$d_i$$$. There are no leap years in Naha.The mood of Coronavirus-chan (and, accordingly, her desire to hug you) depends on the number of the day in a month. In particular, you get $$$j$$$ hugs if you visit Coronavirus-chan on the $$$j$$$-th day of the month.You know about this feature of your friend and want to plan your trip to get as many hugs as possible (and then maybe you can win the heart of Coronavirus-chan). Please note that your trip should not necessarily begin and end in the same year. | [] |
A wise man told Kerem "Different is good" once, so Kerem wants all things in his life to be different. Kerem recently got a string s consisting of lowercase English letters. Since Kerem likes it when things are different, he wants all substrings of his string s to be distinct. Substring is a string formed by some number of consecutive characters of the string. For example, string "aba" has substrings "" (empty substring), "a", "b", "a", "ab", "ba", "aba".If string s has at least two equal substrings then Kerem will change characters at some positions to some other lowercase English letters. Changing characters is a very tiring job, so Kerem want to perform as few changes as possible.Your task is to find the minimum number of changes needed to make all the substrings of the given string distinct, or determine that it is impossible. | ['strings'] |
Winters are just damn freezing cold in Nvodsk! That's why a group of n friends prefers to take a taxi, order a pizza and call girls. The phone numbers in the city consist of three pairs of digits (for example, 12-34-56). Each friend has a phonebook of size si (that's the number of phone numbers). We know that taxi numbers consist of six identical digits (for example, 22-22-22), the numbers of pizza deliveries should necessarily be decreasing sequences of six different digits (for example, 98-73-21), all other numbers are the girls' numbers.You are given your friends' phone books. Calculate which friend is best to go to when you are interested in each of those things (who has maximal number of phone numbers of each type). If the phone book of one person contains some number two times, you should count it twice. That is, each number should be taken into consideration the number of times it occurs in the phone book. | ['strings'] |
You are given an array $$$a_1, a_2, \dots , a_n$$$. Array is good if for each pair of indexes $$$i < j$$$ the condition $$$j - a_j \ne i - a_i$$$ holds. Can you shuffle this array so that it becomes good? To shuffle an array means to reorder its elements arbitrarily (leaving the initial order is also an option).For example, if $$$a = [1, 1, 3, 5]$$$, then shuffled arrays $$$[1, 3, 5, 1]$$$, $$$[3, 5, 1, 1]$$$ and $$$[5, 3, 1, 1]$$$ are good, but shuffled arrays $$$[3, 1, 5, 1]$$$, $$$[1, 1, 3, 5]$$$ and $$$[1, 1, 5, 3]$$$ aren't.It's guaranteed that it's always possible to shuffle an array to meet this condition. | [] |
Magnus decided to play a classic chess game. Though what he saw in his locker shocked him! His favourite chessboard got broken into 4 pieces, each of size n by n, n is always odd. And what's even worse, some squares were of wrong color. j-th square of the i-th row of k-th piece of the board has color ak, i, j; 1 being black and 0 being white. Now Magnus wants to change color of some squares in such a way that he recolors minimum number of squares and obtained pieces form a valid chessboard. Every square has its color different to each of the neightbouring by side squares in a valid board. Its size should be 2n by 2n. You are allowed to move pieces but not allowed to rotate or flip them. | [] |
One day Squidward, Spongebob and Patrick decided to go to the beach. Unfortunately, the weather was bad, so the friends were unable to ride waves. However, they decided to spent their time building sand castles.At the end of the day there were n castles built by friends. Castles are numbered from 1 to n, and the height of the i-th castle is equal to hi. When friends were about to leave, Squidward noticed, that castles are not ordered by their height, and this looks ugly. Now friends are going to reorder the castles in a way to obtain that condition hi ≤ hi + 1 holds for all i from 1 to n - 1.Squidward suggested the following process of sorting castles: Castles are split into blocks — groups of consecutive castles. Therefore the block from i to j will include castles i, i + 1, ..., j. A block may consist of a single castle. The partitioning is chosen in such a way that every castle is a part of exactly one block. Each block is sorted independently from other blocks, that is the sequence hi, hi + 1, ..., hj becomes sorted. The partitioning should satisfy the condition that after each block is sorted, the sequence hi becomes sorted too. This may always be achieved by saying that the whole sequence is a single block. Even Patrick understands that increasing the number of blocks in partitioning will ease the sorting process. Now friends ask you to count the maximum possible number of blocks in a partitioning that satisfies all the above requirements. | [] |
There is a conveyor with $$$120$$$ rows and $$$120$$$ columns. Each row and column is numbered from $$$0$$$ to $$$119$$$, and the cell in $$$i$$$-th row and $$$j$$$-th column is denoted as $$$(i, j)$$$. The top leftmost cell is $$$(0, 0)$$$. Each cell has a belt, and all belts are initially facing to the right.Initially, a slime ball is on the belt of $$$(0, 0)$$$, and other belts are empty. Every second, the state of the conveyor changes as follows: All slime balls on the conveyor move one cell in the direction of the belt at the same time. If there is no cell in the moved position, the slime gets out of the conveyor, and if two slime balls move to the same cell, they merge into one. All belts with slime ball in the previous second change direction at the same time: belts facing to the right become facing to the down, and vice versa. A new slime ball is placed on cell $$$(0, 0)$$$. There are $$$q$$$ queries, each being three integers $$$t$$$, $$$x$$$, and $$$y$$$. You have to find out if there is a slime at the cell $$$(x, y)$$$ after $$$t$$$ seconds from the start. Can you do it? | ['math'] |
— Hey folks, how do you like this problem?— That'll do it. BThero is a powerful magician. He has got $$$n$$$ piles of candies, the $$$i$$$-th pile initially contains $$$a_i$$$ candies. BThero can cast a copy-paste spell as follows: He chooses two piles $$$(i, j)$$$ such that $$$1 \le i, j \le n$$$ and $$$i \ne j$$$. All candies from pile $$$i$$$ are copied into pile $$$j$$$. Formally, the operation $$$a_j := a_j + a_i$$$ is performed. BThero can cast this spell any number of times he wants to — but unfortunately, if some pile contains strictly more than $$$k$$$ candies, he loses his magic power. What is the maximum number of times BThero can cast the spell without losing his power? | ['math'] |
...Once upon a time a man came to the sea. The sea was stormy and dark. The man started to call for the little mermaid to appear but alas, he only woke up Cthulhu...Whereas on the other end of the world Pentagon is actively collecting information trying to predict the monster's behavior and preparing the secret super weapon. Due to high seismic activity and poor weather conditions the satellites haven't yet been able to make clear shots of the monster. The analysis of the first shot resulted in an undirected graph with n vertices and m edges. Now the world's best minds are about to determine whether this graph can be regarded as Cthulhu or not.To add simplicity, let's suppose that Cthulhu looks from the space like some spherical body with tentacles attached to it. Formally, we shall regard as Cthulhu such an undirected graph that can be represented as a set of three or more rooted trees, whose roots are connected by a simple cycle.It is guaranteed that the graph contains no multiple edges and self-loops. | ['graphs'] |
Recently, Tokitsukaze found an interesting game. Tokitsukaze had $$$n$$$ items at the beginning of this game. However, she thought there were too many items, so now she wants to discard $$$m$$$ ($$$1 \le m \le n$$$) special items of them.These $$$n$$$ items are marked with indices from $$$1$$$ to $$$n$$$. In the beginning, the item with index $$$i$$$ is placed on the $$$i$$$-th position. Items are divided into several pages orderly, such that each page contains exactly $$$k$$$ positions and the last positions on the last page may be left empty.Tokitsukaze would do the following operation: focus on the first special page that contains at least one special item, and at one time, Tokitsukaze would discard all special items on this page. After an item is discarded or moved, its old position would be empty, and then the item below it, if exists, would move up to this empty position. The movement may bring many items forward and even into previous pages, so Tokitsukaze would keep waiting until all the items stop moving, and then do the operation (i.e. check the special page and discard the special items) repeatedly until there is no item need to be discarded. Consider the first example from the statement: $$$n=10$$$, $$$m=4$$$, $$$k=5$$$, $$$p=[3, 5, 7, 10]$$$. The are two pages. Initially, the first page is special (since it is the first page containing a special item). So Tokitsukaze discards the special items with indices $$$3$$$ and $$$5$$$. After, the first page remains to be special. It contains $$$[1, 2, 4, 6, 7]$$$, Tokitsukaze discards the special item with index $$$7$$$. After, the second page is special (since it is the first page containing a special item). It contains $$$[9, 10]$$$, Tokitsukaze discards the special item with index $$$10$$$. Tokitsukaze wants to know the number of operations she would do in total. | [] |
You are given three multisets of pairs of colored sticks: $$$R$$$ pairs of red sticks, the first pair has length $$$r_1$$$, the second pair has length $$$r_2$$$, $$$\dots$$$, the $$$R$$$-th pair has length $$$r_R$$$; $$$G$$$ pairs of green sticks, the first pair has length $$$g_1$$$, the second pair has length $$$g_2$$$, $$$\dots$$$, the $$$G$$$-th pair has length $$$g_G$$$; $$$B$$$ pairs of blue sticks, the first pair has length $$$b_1$$$, the second pair has length $$$b_2$$$, $$$\dots$$$, the $$$B$$$-th pair has length $$$b_B$$$; You are constructing rectangles from these pairs of sticks with the following process: take a pair of sticks of one color; take a pair of sticks of another color different from the first one; add the area of the resulting rectangle to the total area. Thus, you get such rectangles that their opposite sides are the same color and their adjacent sides are not the same color.Each pair of sticks can be used at most once, some pairs can be left unused. You are not allowed to split a pair into independent sticks.What is the maximum area you can achieve? | [] |
Calculate the minimum number of characters you need to change in the string s, so that it contains at least k different letters, or print that it is impossible.String s consists only of lowercase Latin letters, and it is allowed to change characters only to lowercase Latin letters too. | ['strings'] |
Ashish has a string $$$s$$$ of length $$$n$$$ containing only characters 'a', 'b' and 'c'.He wants to find the length of the smallest substring, which satisfies the following conditions: Length of the substring is at least $$$2$$$ 'a' occurs strictly more times in this substring than 'b' 'a' occurs strictly more times in this substring than 'c' Ashish is busy planning his next Codeforces round. Help him solve the problem.A string $$$a$$$ is a substring of a string $$$b$$$ if $$$a$$$ can be obtained from $$$b$$$ by deletion of several (possibly, zero or all) characters from the beginning and several (possibly, zero or all) characters from the end. | ['strings'] |
A permutation of length $$$n$$$ is a sequence of integers from $$$1$$$ to $$$n$$$ of length $$$n$$$ containing each number exactly once. For example, $$$[1]$$$, $$$[4, 3, 5, 1, 2]$$$, $$$[3, 2, 1]$$$ are permutations, and $$$[1, 1]$$$, $$$[0, 1]$$$, $$$[2, 2, 1, 4]$$$ are not.There was a permutation $$$p[1 \dots n]$$$. It was merged with itself. In other words, let's take two instances of $$$p$$$ and insert elements of the second $$$p$$$ into the first maintaining relative order of elements. The result is a sequence of the length $$$2n$$$.For example, if $$$p=[3, 1, 2]$$$ some possible results are: $$$[3, 1, 2, 3, 1, 2]$$$, $$$[3, 3, 1, 1, 2, 2]$$$, $$$[3, 1, 3, 1, 2, 2]$$$. The following sequences are not possible results of a merging: $$$[1, 3, 2, 1, 2, 3$$$], [$$$3, 1, 2, 3, 2, 1]$$$, $$$[3, 3, 1, 2, 2, 1]$$$.For example, if $$$p=[2, 1]$$$ the possible results are: $$$[2, 2, 1, 1]$$$, $$$[2, 1, 2, 1]$$$. The following sequences are not possible results of a merging: $$$[1, 1, 2, 2$$$], [$$$2, 1, 1, 2]$$$, $$$[1, 2, 2, 1]$$$.Your task is to restore the permutation $$$p$$$ by the given resulting sequence $$$a$$$. It is guaranteed that the answer exists and is unique.You have to answer $$$t$$$ independent test cases. | [] |
Given an array $$$a$$$ of $$$n$$$ elements, print any value that appears at least three times or print -1 if there is no such value. | [] |
Let $$$F_k$$$ denote the $$$k$$$-th term of Fibonacci sequence, defined as below: $$$F_0 = F_1 = 1$$$ for any integer $$$n \geq 0$$$, $$$F_{n+2} = F_{n+1} + F_n$$$You are given a tree with $$$n$$$ vertices. Recall that a tree is a connected undirected graph without cycles.We call a tree a Fib-tree, if its number of vertices equals $$$F_k$$$ for some $$$k$$$, and at least one of the following conditions holds: The tree consists of only $$$1$$$ vertex; You can divide it into two Fib-trees by removing some edge of the tree. Determine whether the given tree is a Fib-tree or not. | ['number theory', 'trees'] |
Sensation, sensation in the two-dimensional kingdom! The police have caught a highly dangerous outlaw, member of the notorious "Pihters" gang. The law department states that the outlaw was driving from the gang's headquarters in his car when he crashed into an ice cream stall. The stall, the car, and the headquarters each occupies exactly one point on the two-dimensional kingdom.The outlaw's car was equipped with a GPS transmitter. The transmitter showed that the car made exactly n movements on its way from the headquarters to the stall. A movement can move the car from point (x, y) to one of these four points: to point (x - 1, y) which we will mark by letter "L", to point (x + 1, y) — "R", to point (x, y - 1) — "D", to point (x, y + 1) — "U".The GPS transmitter is very inaccurate and it doesn't preserve the exact sequence of the car's movements. Instead, it keeps records of the car's possible movements. Each record is a string of one of these types: "UL", "UR", "DL", "DR" or "ULDR". Each such string means that the car made a single movement corresponding to one of the characters of the string. For example, string "UL" means that the car moved either "U", or "L".You've received the journal with the outlaw's possible movements from the headquarters to the stall. The journal records are given in a chronological order. Given that the ice-cream stall is located at point (0, 0), your task is to print the number of different points that can contain the gang headquarters (that is, the number of different possible locations of the car's origin). | ['math'] |
Devu being a small kid, likes to play a lot, but he only likes to play with arrays. While playing he came up with an interesting question which he could not solve, can you please solve it for him?Given an array consisting of distinct integers. Is it possible to partition the whole array into k disjoint non-empty parts such that p of the parts have even sum (each of them must have even sum) and remaining k - p have odd sum? (note that parts need not to be continuous).If it is possible to partition the array, also give any possible way of valid partitioning. | ['number theory'] |
For given n, l and r find the number of distinct geometrical progression, each of which contains n distinct integers not less than l and not greater than r. In other words, for each progression the following must hold: l ≤ ai ≤ r and ai ≠ aj , where a1, a2, ..., an is the geometrical progression, 1 ≤ i, j ≤ n and i ≠ j.Geometrical progression is a sequence of numbers a1, a2, ..., an where each term after first is found by multiplying the previous one by a fixed non-zero number d called the common ratio. Note that in our task d may be non-integer. For example in progression 4, 6, 9, common ratio is .Two progressions a1, a2, ..., an and b1, b2, ..., bn are considered different, if there is such i (1 ≤ i ≤ n) that ai ≠ bi. | ['math', 'number theory'] |
You are given a chessboard consisting of $$$n$$$ rows and $$$n$$$ columns. Rows are numbered from bottom to top from $$$1$$$ to $$$n$$$. Columns are numbered from left to right from $$$1$$$ to $$$n$$$. The cell at the intersection of the $$$x$$$-th column and the $$$y$$$-th row is denoted as $$$(x, y)$$$. Furthermore, the $$$k$$$-th column is a special column. Initially, the board is empty. There are $$$m$$$ changes to the board. During the $$$i$$$-th change one pawn is added or removed from the board. The current board is good if we can move all pawns to the special column by the followings rules: Pawn in the cell $$$(x, y)$$$ can be moved to the cell $$$(x, y + 1)$$$, $$$(x - 1, y + 1)$$$ or $$$(x + 1, y + 1)$$$; You can make as many such moves as you like; Pawns can not be moved outside the chessboard; Each cell can not contain more than one pawn. The current board may not always be good. To fix it, you can add new rows to the board. New rows are added at the top, i. e. they will have numbers $$$n+1, n+2, n+3, \dots$$$.After each of $$$m$$$ changes, print one integer — the minimum number of rows which you have to add to make the board good. | [] |
Andrew skipped lessons on the subject 'Algorithms and Data Structures' for the entire term. When he came to the final test, the teacher decided to give him a difficult task as a punishment.The teacher gave Andrew an array of n numbers a1, ..., an. After that he asked Andrew for each k from 1 to n - 1 to build a k-ary heap on the array and count the number of elements for which the property of the minimum-rooted heap is violated, i.e. the value of an element is less than the value of its parent.Andrew looked up on the Wikipedia that a k-ary heap is a rooted tree with vertices in elements of the array. If the elements of the array are indexed from 1 to n, then the children of element v are elements with indices k(v - 1) + 2, ..., kv + 1 (if some of these elements lie outside the borders of the array, the corresponding children are absent). In any k-ary heap every element except for the first one has exactly one parent; for the element 1 the parent is absent (this element is the root of the heap). Denote p(v) as the number of the parent of the element with the number v. Let's say that for a non-root element v the property of the heap is violated if av < ap(v).Help Andrew cope with the task! | ['math'] |
This is a hard version of the problem. The actual problems are different, but the easy version is almost a subtask of the hard version. Note that the constraints and the output format are different.You are given a string $$$s$$$ consisting of $$$n$$$ lowercase Latin letters.You have to color all its characters the minimum number of colors (each character to exactly one color, the same letters can be colored the same or different colors, i.e. you can choose exactly one color for each index in $$$s$$$).After coloring, you can swap any two neighboring characters of the string that are colored different colors. You can perform such an operation arbitrary (possibly, zero) number of times.The goal is to make the string sorted, i.e. all characters should be in alphabetical order.Your task is to find the minimum number of colors which you have to color the given string in so that after coloring it can become sorted by some sequence of swaps. Note that you have to restore only coloring, not the sequence of swaps. | [] |
Bob is a farmer. He has a large pasture with many sheep. Recently, he has lost some of them due to wolf attacks. He thus decided to place some shepherd dogs in such a way that all his sheep are protected.The pasture is a rectangle consisting of R × C cells. Each cell is either empty, contains a sheep, a wolf or a dog. Sheep and dogs always stay in place, but wolves can roam freely around the pasture, by repeatedly moving to the left, right, up or down to a neighboring cell. When a wolf enters a cell with a sheep, it consumes it. However, no wolf can enter a cell with a dog.Initially there are no dogs. Place dogs onto the pasture in such a way that no wolf can reach any sheep, or determine that it is impossible. Note that since you have many dogs, you do not need to minimize their number. | ['graphs'] |
A non-empty string is called palindrome, if it reads the same from the left to the right and from the right to the left. For example, "abcba", "a", and "abba" are palindromes, while "abab" and "xy" are not.A string is called a substring of another string, if it can be obtained from that string by dropping some (possibly zero) number of characters from the beginning and from the end of it. For example, "abc", "ab", and "c" are substrings of the string "abc", while "ac" and "d" are not.Let's define a palindromic count of the string as the number of its substrings that are palindromes. For example, the palindromic count of the string "aaa" is $$$6$$$ because all its substrings are palindromes, and the palindromic count of the string "abc" is $$$3$$$ because only its substrings of length $$$1$$$ are palindromes.You are given a string $$$s$$$. You can arbitrarily rearrange its characters. You goal is to obtain a string with the maximum possible value of palindromic count. | [] |
Polycarp has found a table having an infinite number of rows and columns. The rows are numbered from $$$1$$$, starting from the topmost one. The columns are numbered from $$$1$$$, starting from the leftmost one.Initially, the table hasn't been filled and Polycarp wants to fix it. He writes integers from $$$1$$$ and so on to the table as follows. The figure shows the placement of the numbers from $$$1$$$ to $$$10$$$. The following actions are denoted by the arrows. The leftmost topmost cell of the table is filled with the number $$$1$$$. Then he writes in the table all positive integers beginning from $$$2$$$ sequentially using the following algorithm.First, Polycarp selects the leftmost non-filled cell in the first row and fills it. Then, while the left neighbor of the last filled cell is filled, he goes down and fills the next cell. So he goes down until the last filled cell has a non-filled neighbor to the left (look at the vertical arrow going down in the figure above).After that, he fills the cells from the right to the left until he stops at the first column (look at the horizontal row in the figure above). Then Polycarp selects the leftmost non-filled cell in the first row, goes down, and so on.A friend of Polycarp has a favorite number $$$k$$$. He wants to know which cell will contain the number. Help him to find the indices of the row and the column, such that the intersection of the row and the column is the cell containing the number $$$k$$$. | ['math'] |
Theofanis started playing the new online game called "Among them". However, he always plays with Cypriot players, and they all have the same name: "Andreas" (the most common name in Cyprus).In each game, Theofanis plays with $$$n$$$ other players. Since they all have the same name, they are numbered from $$$1$$$ to $$$n$$$.The players write $$$m$$$ comments in the chat. A comment has the structure of "$$$i$$$ $$$j$$$ $$$c$$$" where $$$i$$$ and $$$j$$$ are two distinct integers and $$$c$$$ is a string ($$$1 \le i, j \le n$$$; $$$i \neq j$$$; $$$c$$$ is either imposter or crewmate). The comment means that player $$$i$$$ said that player $$$j$$$ has the role $$$c$$$.An imposter always lies, and a crewmate always tells the truth. Help Theofanis find the maximum possible number of imposters among all the other Cypriot players, or determine that the comments contradict each other (see the notes for further explanation).Note that each player has exactly one role: either imposter or crewmate. | ['graphs'] |
You are given two lists of segments $$$[al_1, ar_1], [al_2, ar_2], \dots, [al_n, ar_n]$$$ and $$$[bl_1, br_1], [bl_2, br_2], \dots, [bl_n, br_n]$$$.Initially, all segments $$$[al_i, ar_i]$$$ are equal to $$$[l_1, r_1]$$$ and all segments $$$[bl_i, br_i]$$$ are equal to $$$[l_2, r_2]$$$.In one step, you can choose one segment (either from the first or from the second list) and extend it by $$$1$$$. In other words, suppose you've chosen segment $$$[x, y]$$$ then you can transform it either into $$$[x - 1, y]$$$ or into $$$[x, y + 1]$$$.Let's define a total intersection $$$I$$$ as the sum of lengths of intersections of the corresponding pairs of segments, i.e. $$$\sum\limits_{i=1}^{n}{\text{intersection_length}([al_i, ar_i], [bl_i, br_i])}$$$. Empty intersection has length $$$0$$$ and length of a segment $$$[x, y]$$$ is equal to $$$y - x$$$.What is the minimum number of steps you need to make $$$I$$$ greater or equal to $$$k$$$? | ['math'] |
There is a fence in front of Polycarpus's home. The fence consists of n planks of the same width which go one after another from left to right. The height of the i-th plank is hi meters, distinct planks can have distinct heights. Fence for n = 7 and h = [1, 2, 6, 1, 1, 7, 1] Polycarpus has bought a posh piano and is thinking about how to get it into the house. In order to carry out his plan, he needs to take exactly k consecutive planks from the fence. Higher planks are harder to tear off the fence, so Polycarpus wants to find such k consecutive planks that the sum of their heights is minimal possible.Write the program that finds the indexes of k consecutive planks with minimal total height. Pay attention, the fence is not around Polycarpus's home, it is in front of home (in other words, the fence isn't cyclic). | [] |
You are playing a computer card game called Splay the Sire. Currently you are struggling to defeat the final boss of the game.The boss battle consists of $$$n$$$ turns. During each turn, you will get several cards. Each card has two parameters: its cost $$$c_i$$$ and damage $$$d_i$$$. You may play some of your cards during each turn in some sequence (you choose the cards and the exact order they are played), as long as the total cost of the cards you play during the turn does not exceed $$$3$$$. After playing some (possibly zero) cards, you end your turn, and all cards you didn't play are discarded. Note that you can use each card at most once.Your character has also found an artifact that boosts the damage of some of your actions: every $$$10$$$-th card you play deals double damage.What is the maximum possible damage you can deal during $$$n$$$ turns? | [] |
Orac is studying number theory, and he is interested in the properties of divisors.For two positive integers $$$a$$$ and $$$b$$$, $$$a$$$ is a divisor of $$$b$$$ if and only if there exists an integer $$$c$$$, such that $$$a\cdot c=b$$$.For $$$n \ge 2$$$, we will denote as $$$f(n)$$$ the smallest positive divisor of $$$n$$$, except $$$1$$$.For example, $$$f(7)=7,f(10)=2,f(35)=5$$$.For the fixed integer $$$n$$$, Orac decided to add $$$f(n)$$$ to $$$n$$$. For example, if he had an integer $$$n=5$$$, the new value of $$$n$$$ will be equal to $$$10$$$. And if he had an integer $$$n=6$$$, $$$n$$$ will be changed to $$$8$$$.Orac loved it so much, so he decided to repeat this operation several times.Now, for two positive integers $$$n$$$ and $$$k$$$, Orac asked you to add $$$f(n)$$$ to $$$n$$$ exactly $$$k$$$ times (note that $$$n$$$ will change after each operation, so $$$f(n)$$$ may change too) and tell him the final value of $$$n$$$.For example, if Orac gives you $$$n=5$$$ and $$$k=2$$$, at first you should add $$$f(5)=5$$$ to $$$n=5$$$, so your new value of $$$n$$$ will be equal to $$$n=10$$$, after that, you should add $$$f(10)=2$$$ to $$$10$$$, so your new (and the final!) value of $$$n$$$ will be equal to $$$12$$$.Orac may ask you these queries many times. | ['math'] |
You are given a string s consisting of lowercase Latin letters. Character c is called k-dominant iff each substring of s with length at least k contains this character c.You have to find minimum k such that there exists at least one k-dominant character. | [] |
Dima is a good person. In fact, he's great. But all good things come to an end...Seryozha is going to kick Dima just few times.. For this reason he divides the room into unit squares. Now the room is a rectangle n × m consisting of unit squares.For the beginning, Seryozha put Dima in a center of some square. Then he started to kick Dima (it is known, that he kicks Dima at least once). Each time when Dima is kicked he flyes up and moves into one of four directions (up, left, right, down). On each move Dima passes k (k > 1) unit of the length in the corresponding direction. Seryozha is really kind, so he kicks Dima in such way that Dima never meets the walls (in other words, Dima never leave the room's space). Seryozha is also dynamic character so Dima never flies above the same segment, connecting a pair of adjacent squares, twice.Seryozha kicks Dima for a long time, but Dima is not vindictive — Dima writes. Dima marked all squares in which he was staying or above which he was flying. Thanks to kicks, Dima does not remember the k value, so he asks you to find all possible values which matches to the Dima's records. | ['graphs'] |
We just discovered a new data structure in our research group: a suffix three!It's very useful for natural language processing. Given three languages and three suffixes, a suffix three can determine which language a sentence is written in.It's super simple, 100% accurate, and doesn't involve advanced machine learning algorithms.Let us tell you how it works. If a sentence ends with "po" the language is Filipino. If a sentence ends with "desu" or "masu" the language is Japanese. If a sentence ends with "mnida" the language is Korean. Given this, we need you to implement a suffix three that can differentiate Filipino, Japanese, and Korean.Oh, did I say three suffixes? I meant four. | [] |
After rejecting $$$10^{100}$$$ data structure problems, Errorgorn is very angry at Anton and decided to kill him.Anton's DNA can be represented as a string $$$a$$$ which only contains the characters "ANTON" (there are only $$$4$$$ distinct characters). Errorgorn can change Anton's DNA into string $$$b$$$ which must be a permutation of $$$a$$$. However, Anton's body can defend against this attack. In $$$1$$$ second, his body can swap $$$2$$$ adjacent characters of his DNA to transform it back to $$$a$$$. Anton's body is smart and will use the minimum number of moves.To maximize the chance of Anton dying, Errorgorn wants to change Anton's DNA the string that maximizes the time for Anton's body to revert his DNA. But since Errorgorn is busy making more data structure problems, he needs your help to find the best string $$$B$$$. Can you help him? | ['math', 'strings'] |
Vasya has recently found out what a digital root of a number is and he decided to share his knowledge with you.Let's assume that S(n) is the sum of digits of number n, for example, S(4098) = 4 + 0 + 9 + 8 = 21. Then the digital root of number n equals to: dr(n) = S(n), if S(n) < 10; dr(n) = dr( S(n) ), if S(n) ≥ 10. For example, dr(4098) = dr(21) = 3.Vasya is afraid of large numbers, so the numbers he works with are at most 101000. For all such numbers, he has proved that dr(n) = S( S( S( S(n) ) ) ) (n ≤ 101000).Now Vasya wants to quickly find numbers with the given digital root. The problem is, he hasn't learned how to do that and he asked you to help him. You task is, given numbers k and d, find the number consisting of exactly k digits (the leading zeroes are not allowed), with digital root equal to d, or else state that such number does not exist. | [] |
You are given an integer $$$n$$$. In one move, you can either multiply $$$n$$$ by two or divide $$$n$$$ by $$$6$$$ (if it is divisible by $$$6$$$ without the remainder).Your task is to find the minimum number of moves needed to obtain $$$1$$$ from $$$n$$$ or determine if it's impossible to do that.You have to answer $$$t$$$ independent test cases. | ['math'] |
You are given a sequence of $$$n$$$ integers $$$a_1, a_2, \ldots, a_n$$$.You have to construct two sequences of integers $$$b$$$ and $$$c$$$ with length $$$n$$$ that satisfy: for every $$$i$$$ ($$$1\leq i\leq n$$$) $$$b_i+c_i=a_i$$$ $$$b$$$ is non-decreasing, which means that for every $$$1<i\leq n$$$, $$$b_i\geq b_{i-1}$$$ must hold $$$c$$$ is non-increasing, which means that for every $$$1<i\leq n$$$, $$$c_i\leq c_{i-1}$$$ must hold You have to minimize $$$\max(b_i,c_i)$$$. In other words, you have to minimize the maximum number in sequences $$$b$$$ and $$$c$$$.Also there will be $$$q$$$ changes, the $$$i$$$-th change is described by three integers $$$l,r,x$$$. You should add $$$x$$$ to $$$a_l,a_{l+1}, \ldots, a_r$$$. You have to find the minimum possible value of $$$\max(b_i,c_i)$$$ for the initial sequence and for sequence after each change. | ['math'] |
Meanwhile, the kingdom of K is getting ready for the marriage of the King's daughter. However, in order not to lose face in front of the relatives, the King should first finish reforms in his kingdom. As the King can not wait for his daughter's marriage, reforms must be finished as soon as possible.The kingdom currently consists of n cities. Cities are connected by n - 1 bidirectional road, such that one can get from any city to any other city. As the King had to save a lot, there is only one path between any two cities.What is the point of the reform? The key ministries of the state should be relocated to distinct cities (we call such cities important). However, due to the fact that there is a high risk of an attack by barbarians it must be done carefully. The King has made several plans, each of which is described by a set of important cities, and now wonders what is the best plan.Barbarians can capture some of the cities that are not important (the important ones will have enough protection for sure), after that the captured city becomes impassable. In particular, an interesting feature of the plan is the minimum number of cities that the barbarians need to capture in order to make all the important cities isolated, that is, from all important cities it would be impossible to reach any other important city.Help the King to calculate this characteristic for each of his plan. | ['graphs', 'trees'] |
The only difference between the easy and hard versions is the constraints on the number of queries.This is an interactive problem.Ridbit has a hidden array $$$a$$$ of $$$n$$$ integers which he wants Ashish to guess. Note that $$$n$$$ is a power of two. Ashish is allowed to ask three different types of queries. They are of the form AND $$$i$$$ $$$j$$$: ask for the bitwise AND of elements $$$a_i$$$ and $$$a_j$$$ $$$(1 \leq i, j \le n$$$, $$$i \neq j)$$$ OR $$$i$$$ $$$j$$$: ask for the bitwise OR of elements $$$a_i$$$ and $$$a_j$$$ $$$(1 \leq i, j \le n$$$, $$$i \neq j)$$$ XOR $$$i$$$ $$$j$$$: ask for the bitwise XOR of elements $$$a_i$$$ and $$$a_j$$$ $$$(1 \leq i, j \le n$$$, $$$i \neq j)$$$ Can you help Ashish guess the elements of the array?In this version, each element takes a value in the range $$$[0, n-1]$$$ (inclusive) and Ashish can ask no more than $$$n+1$$$ queries. | ['math'] |
Pikachu had an array with him. He wrote down all the non-empty subsequences of the array on paper. Note that an array of size n has 2n - 1 non-empty subsequences in it. Pikachu being mischievous as he always is, removed all the subsequences in which Maximum_element_of_the_subsequence - Minimum_element_of_subsequence ≥ dPikachu was finally left with X subsequences. However, he lost the initial array he had, and now is in serious trouble. He still remembers the numbers X and d. He now wants you to construct any such array which will satisfy the above conditions. All the numbers in the final array should be positive integers less than 1018. Note the number of elements in the output array should not be more than 104. If no answer is possible, print - 1. | [] |
Polycarp was recently given a set of $$$n$$$ (number $$$n$$$ — even) dominoes. Each domino contains two integers from $$$1$$$ to $$$n$$$.Can he divide all the dominoes into two sets so that all the numbers on the dominoes of each set are different? Each domino must go into exactly one of the two sets.For example, if he has $$$4$$$ dominoes: $$$\{1, 4\}$$$, $$$\{1, 3\}$$$, $$$\{3, 2\}$$$ and $$$\{4, 2\}$$$, then Polycarp will be able to divide them into two sets in the required way. The first set can include the first and third dominoes ($$$\{1, 4\}$$$ and $$$\{3, 2\}$$$), and the second set — the second and fourth ones ($$$\{1, 3\}$$$ and $$$\{4, 2\}$$$). | ['graphs'] |
The Resistance is trying to take control over as many planets of a particular solar system as possible. Princess Heidi is in charge of the fleet, and she must send ships to some planets in order to maximize the number of controlled planets.The Galaxy contains N planets, connected by bidirectional hyperspace tunnels in such a way that there is a unique path between every pair of the planets.A planet is controlled by the Resistance if there is a Resistance ship in its orbit, or if the planet lies on the shortest path between some two planets that have Resistance ships in their orbits.Heidi has not yet made up her mind as to how many ships to use. Therefore, she is asking you to compute, for every K = 1, 2, 3, ..., N, the maximum number of planets that can be controlled with a fleet consisting of K ships. | ['graphs', 'trees'] |
You are given a string $$$s$$$ consisting of exactly $$$n$$$ characters, and each character is either '0', '1' or '2'. Such strings are called ternary strings.Your task is to replace minimum number of characters in this string with other characters to obtain a balanced ternary string (balanced ternary string is a ternary string such that the number of characters '0' in this string is equal to the number of characters '1', and the number of characters '1' (and '0' obviously) is equal to the number of characters '2').Among all possible balanced ternary strings you have to obtain the lexicographically (alphabetically) smallest.Note that you can neither remove characters from the string nor add characters to the string. Also note that you can replace the given characters only with characters '0', '1' and '2'.It is guaranteed that the answer exists. | ['strings'] |
DZY loves planting, and he enjoys solving tree problems.DZY has a weighted tree (connected undirected graph without cycles) containing n nodes (they are numbered from 1 to n). He defines the function g(x, y) (1 ≤ x, y ≤ n) as the longest edge in the shortest path between nodes x and y. Specially g(z, z) = 0 for every z.For every integer sequence p1, p2, ..., pn (1 ≤ pi ≤ n), DZY defines f(p) as . DZY wants to find such a sequence p that f(p) has maximum possible value. But there is one more restriction: the element j can appear in p at most xj times.Please, find the maximum possible f(p) under the described restrictions. | ['trees'] |
You have a binary string $$$a$$$ of length $$$n$$$ consisting only of digits $$$0$$$ and $$$1$$$. You are given $$$q$$$ queries. In the $$$i$$$-th query, you are given two indices $$$l$$$ and $$$r$$$ such that $$$1 \le l \le r \le n$$$. Let $$$s=a[l,r]$$$. You are allowed to do the following operation on $$$s$$$: Choose two indices $$$x$$$ and $$$y$$$ such that $$$1 \le x \le y \le |s|$$$. Let $$$t$$$ be the substring $$$t = s[x, y]$$$. Then for all $$$1 \le i \le |t| - 1$$$, the condition $$$t_i \neq t_{i+1}$$$ has to hold. Note that $$$x = y$$$ is always a valid substring. Delete the substring $$$s[x, y]$$$ from $$$s$$$. For each of the $$$q$$$ queries, find the minimum number of operations needed to make $$$s$$$ an empty string.Note that for a string $$$s$$$, $$$s[l,r]$$$ denotes the subsegment $$$s_l,s_{l+1},\ldots,s_r$$$. | [] |
Monocarp plays "Rage of Empires II: Definitive Edition" — a strategic computer game. Right now he's planning to attack his opponent in the game, but Monocarp's forces cannot enter the opponent's territory since the opponent has built a wall.The wall consists of $$$n$$$ sections, aligned in a row. The $$$i$$$-th section initially has durability $$$a_i$$$. If durability of some section becomes $$$0$$$ or less, this section is considered broken.To attack the opponent, Monocarp needs to break at least two sections of the wall (any two sections: possibly adjacent, possibly not). To do this, he plans to use an onager — a special siege weapon. The onager can be used to shoot any section of the wall; the shot deals $$$2$$$ damage to the target section and $$$1$$$ damage to adjacent sections. In other words, if the onager shoots at the section $$$x$$$, then the durability of the section $$$x$$$ decreases by $$$2$$$, and the durability of the sections $$$x - 1$$$ and $$$x + 1$$$ (if they exist) decreases by $$$1$$$ each. Monocarp can shoot at any sections any number of times, he can even shoot at broken sections.Monocarp wants to calculate the minimum number of onager shots needed to break at least two sections. Help him! | ['math'] |
You are given a sequence $$$a_1, a_2, \dots, a_n$$$, consisting of integers.You can apply the following operation to this sequence: choose some integer $$$x$$$ and move all elements equal to $$$x$$$ either to the beginning, or to the end of $$$a$$$. Note that you have to move all these elements in one direction in one operation.For example, if $$$a = [2, 1, 3, 1, 1, 3, 2]$$$, you can get the following sequences in one operation (for convenience, denote elements equal to $$$x$$$ as $$$x$$$-elements): $$$[1, 1, 1, 2, 3, 3, 2]$$$ if you move all $$$1$$$-elements to the beginning; $$$[2, 3, 3, 2, 1, 1, 1]$$$ if you move all $$$1$$$-elements to the end; $$$[2, 2, 1, 3, 1, 1, 3]$$$ if you move all $$$2$$$-elements to the beginning; $$$[1, 3, 1, 1, 3, 2, 2]$$$ if you move all $$$2$$$-elements to the end; $$$[3, 3, 2, 1, 1, 1, 2]$$$ if you move all $$$3$$$-elements to the beginning; $$$[2, 1, 1, 1, 2, 3, 3]$$$ if you move all $$$3$$$-elements to the end; You have to determine the minimum number of such operations so that the sequence $$$a$$$ becomes sorted in non-descending order. Non-descending order means that for all $$$i$$$ from $$$2$$$ to $$$n$$$, the condition $$$a_{i-1} \le a_i$$$ is satisfied.Note that you have to answer $$$q$$$ independent queries. | [] |
In a building where Polycarp lives there are equal number of flats on each floor. Unfortunately, Polycarp don't remember how many flats are on each floor, but he remembers that the flats are numbered from 1 from lower to upper floors. That is, the first several flats are on the first floor, the next several flats are on the second and so on. Polycarp don't remember the total number of flats in the building, so you can consider the building to be infinitely high (i.e. there are infinitely many floors). Note that the floors are numbered from 1.Polycarp remembers on which floors several flats are located. It is guaranteed that this information is not self-contradictory. It means that there exists a building with equal number of flats on each floor so that the flats from Polycarp's memory have the floors Polycarp remembers.Given this information, is it possible to restore the exact floor for flat n? | [] |
A new agent called Killjoy invented a virus COVID-2069 that infects accounts on Codeforces. Each account has a rating, described by an integer (it can possibly be negative or very large).Killjoy's account is already infected and has a rating equal to $$$x$$$. Its rating is constant. There are $$$n$$$ accounts except hers, numbered from $$$1$$$ to $$$n$$$. The $$$i$$$-th account's initial rating is $$$a_i$$$. Any infected account (initially the only infected account is Killjoy's) instantly infects any uninfected account if their ratings are equal. This can happen at the beginning (before any rating changes) and after each contest. If an account is infected, it can not be healed.Contests are regularly held on Codeforces. In each contest, any of these $$$n$$$ accounts (including infected ones) can participate. Killjoy can't participate. After each contest ratings are changed this way: each participant's rating is changed by an integer, but the sum of all changes must be equal to zero. New ratings can be any integer.Find out the minimal number of contests needed to infect all accounts. You can choose which accounts will participate in each contest and how the ratings will change.It can be proven that all accounts can be infected in some finite number of contests. | ['math'] |
Ivan wants to write a letter to his friend. The letter is a string s consisting of lowercase Latin letters.Unfortunately, when Ivan started writing the letter, he realised that it is very long and writing the whole letter may take extremely long time. So he wants to write the compressed version of string s instead of the string itself.The compressed version of string s is a sequence of strings c1, s1, c2, s2, ..., ck, sk, where ci is the decimal representation of number ai (without any leading zeroes) and si is some string consisting of lowercase Latin letters. If Ivan writes string s1 exactly a1 times, then string s2 exactly a2 times, and so on, the result will be string s.The length of a compressed version is |c1| + |s1| + |c2| + |s2|... |ck| + |sk|. Among all compressed versions Ivan wants to choose a version such that its length is minimum possible. Help Ivan to determine minimum possible length. | ['strings'] |
Limak is a little bear who learns to draw. People usually start with houses, fences and flowers but why would bears do it? Limak lives in the forest and he decides to draw a tree.Recall that tree is a connected graph consisting of n vertices and n - 1 edges.Limak chose a tree with n vertices. He has infinite strip of paper with two parallel rows of dots. Little bear wants to assign vertices of a tree to some n distinct dots on a paper so that edges would intersect only at their endpoints — drawn tree must be planar. Below you can see one of correct drawings for the first sample test. Is it possible for Limak to draw chosen tree? | [] |
You are given a string $$$s$$$, consisting of lowercase Latin letters. Every letter appears in it no more than twice.Your task is to rearrange the letters in the string in such a way that for each pair of letters that appear exactly twice, the distance between the letters in the pair is the same. You are not allowed to add or remove letters.It can be shown that the answer always exists. If there are multiple answers, print any of them. | [] |
Omkar is playing his favorite pixelated video game, Bed Wars! In Bed Wars, there are $$$n$$$ players arranged in a circle, so that for all $$$j$$$ such that $$$2 \leq j \leq n$$$, player $$$j - 1$$$ is to the left of the player $$$j$$$, and player $$$j$$$ is to the right of player $$$j - 1$$$. Additionally, player $$$n$$$ is to the left of player $$$1$$$, and player $$$1$$$ is to the right of player $$$n$$$.Currently, each player is attacking either the player to their left or the player to their right. This means that each player is currently being attacked by either $$$0$$$, $$$1$$$, or $$$2$$$ other players. A key element of Bed Wars strategy is that if a player is being attacked by exactly $$$1$$$ other player, then they should logically attack that player in response. If instead a player is being attacked by $$$0$$$ or $$$2$$$ other players, then Bed Wars strategy says that the player can logically attack either of the adjacent players.Unfortunately, it might be that some players in this game are not following Bed Wars strategy correctly. Omkar is aware of whom each player is currently attacking, and he can talk to any amount of the $$$n$$$ players in the game to make them instead attack another player — i. e. if they are currently attacking the player to their left, Omkar can convince them to instead attack the player to their right; if they are currently attacking the player to their right, Omkar can convince them to instead attack the player to their left. Omkar would like all players to be acting logically. Calculate the minimum amount of players that Omkar needs to talk to so that after all players he talked to (if any) have changed which player they are attacking, all players are acting logically according to Bed Wars strategy. | [] |
Furik loves math lessons very much, so he doesn't attend them, unlike Rubik. But now Furik wants to get a good mark for math. For that Ms. Ivanova, his math teacher, gave him a new task. Furik solved the task immediately. Can you?You are given a set of digits, your task is to find the maximum integer that you can make from these digits. The made number must be divisible by 2, 3, 5 without a residue. It is permitted to use not all digits from the set, it is forbidden to use leading zeroes.Each digit is allowed to occur in the number the same number of times it occurs in the set. | ['math'] |
After a successful year of milk production, Farmer John is rewarding his cows with their favorite treat: tasty grass!On the field, there is a row of $$$n$$$ units of grass, each with a sweetness $$$s_i$$$. Farmer John has $$$m$$$ cows, each with a favorite sweetness $$$f_i$$$ and a hunger value $$$h_i$$$. He would like to pick two disjoint subsets of cows to line up on the left and right side of the grass row. There is no restriction on how many cows must be on either side. The cows will be treated in the following manner: The cows from the left and right side will take turns feeding in an order decided by Farmer John. When a cow feeds, it walks towards the other end without changing direction and eats grass of its favorite sweetness until it eats $$$h_i$$$ units. The moment a cow eats $$$h_i$$$ units, it will fall asleep there, preventing further cows from passing it from both directions. If it encounters another sleeping cow or reaches the end of the grass row, it will get upset. Farmer John absolutely does not want any cows to get upset. Note that grass does not grow back. Also, to prevent cows from getting upset, not every cow has to feed since FJ can choose a subset of them. Surprisingly, FJ has determined that sleeping cows are the most satisfied. If FJ orders optimally, what is the maximum number of sleeping cows that can result, and how many ways can FJ choose the subset of cows on the left and right side to achieve that maximum number of sleeping cows (modulo $$$10^9+7$$$)? The order in which FJ sends the cows does not matter as long as no cows get upset. | ['math'] |
One day Polycarp decided to rewatch his absolute favourite episode of well-known TV series "Tufurama". He was pretty surprised when he got results only for season 7 episode 3 with his search query of "Watch Tufurama season 3 episode 7 online full hd free". This got Polycarp confused — what if he decides to rewatch the entire series someday and won't be able to find the right episodes to watch? Polycarp now wants to count the number of times he will be forced to search for an episode using some different method.TV series have n seasons (numbered 1 through n), the i-th season has ai episodes (numbered 1 through ai). Polycarp thinks that if for some pair of integers x and y (x < y) exist both season x episode y and season y episode x then one of these search queries will include the wrong results. Help Polycarp to calculate the number of such pairs! | [] |
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