时间：2021-07-01 10:21:17 帮助过：31人阅读
B：分别写出来1，2，3，4，的n次方对5取余。你会发现和对5取余有一个循环节。如果%4 = 0，输出4，否则输出0.
写一个大数取余就过了。
B. Fedya and Maths
time limit per test
1 second
memory limit per test
256 megabytes
input
standard input
output
standard output
Fedya studies in a gymnasium. Fedya's maths hometask is to calculate the following expression:
(1n?+?2n?+?3n?+?4n) mod 5for given value of n. Fedya managed to complete the task. Can you? Note that given number n can be extremely large (e.g. it can exceed any integer type of your programming language).
Input
The single line contains a single integer n (0?≤?n?≤?10105). The number doesn't contain any leading zeroes.
Output
Print the value of the expression without leading zeros.
Sample test(s)
input
output
input
124356983594583453458888889
output
Note
Operation x mod y means taking remainder after division x by y.
Note to the first sample:
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先根据数字进行哈希，然后线性的dp一遍，dp[i][1] = ma(dp[i-2][0], dp[i-2][1]) + vis[i]*i,dp[i][0] = max(dp[i-1][0], dp[i-1][1]).1代表取这个数，0代表不取。注意数据类型要用long long。
C. Boredom
time limit per test
1 second
memory limit per test
256 megabytes
input
standard input
output
standard output
Alex doesn't like boredom. That's why whenever he gets bored, he comes up with games. One long winter evening he came up with a game and decided to play it.
Given a sequence a consisting of n integers. The player can make several steps. In a single step he can choose an element of the sequence (let's denote it ak) and delete it, at that all elements equal to ak?+?1 and ak?-?1 also must be deleted from the sequence. That step brings ak points to the player.
Alex is a perfectionist, so he decided to get as many points as possible. Help him.
Input
The first line contains integer n (1?≤?n?≤?105) that shows how many numbers are in Alex's sequence.
The second line contains n integers a1, a2, ..., an (1?≤?ai?≤?105).
Output
Print a single integer ? the maximum number of points that Alex can earn.
Sample test(s)
input
21 2
output
input
31 2 3
output
input
91 2 1 3 2 2 2 2 3
output
10
Note
Consider the third test example. At first step we need to choose any element equal to 2. After that step our sequence looks like this [2,?2,?2,?2]. Then we do 4 steps, on each step we choose any element equals to 2. In total we earn 10 points.
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