Functions again

题意翻译

定义一个函数，函数如下： $f[l,r]=\sum^{r-1}_{i=l}|a_i-a_{i+1}|\times (-1)^{i-l}$ 1<=l,r<=n |x|表示x的绝对值。 现在给你一个函数，请取恰当的l,r使f值最大，请输出最大的f值

题目描述

Something happened in Uzhlyandia again... There are riots on the streets... Famous Uzhlyandian superheroes Shean the Sheep and Stas the Giraffe were called in order to save the situation. Upon the arriving, they found that citizens are worried about maximum values of the Main Uzhlyandian Function $ f $ , which is defined as follows: In the above formula, $ 1<=l&lt;r<=n $ must hold, where $ n $ is the size of the Main Uzhlyandian Array $ a $ , and $ |x| $ means absolute value of $ x $ . But the heroes skipped their math lessons in school, so they asked you for help. Help them calculate the maximum value of $ f $ among all possible values of $ l $ and $ r $ for the given array $ a $ .

输入输出格式

输入格式

The first line contains single integer $ n $ ( $ 2<=n<=10^{5} $ ) — the size of the array $ a $ . The second line contains $ n $ integers $ a_{1},a_{2},...,a_{n} $ (- $ 10^{9}<=a_{i}<=10^{9} $ ) — the array elements.

输出格式

Print the only integer — the maximum value of $ f $ .

输入输出样例

输入样例 #1

5
1 4 2 3 1

输出样例 #1

3

输入样例 #2

4
1 5 4 7

输出样例 #2

6

说明

In the first sample case, the optimal value of $ f $ is reached on intervals $ [1,2] $ and $ [2,5] $ . In the second case maximal value of $ f $ is reachable only on the whole array.