Little Elephant and Sorting

题意翻译

给你 $n$ 个数，定义一次操作：任选一个区间 $+1$ ，目的是让后一个数不能小于前一个数（不下降子序列），然后最小操作数是多少？

题目描述

The Little Elephant loves sortings. He has an array $ a $ consisting of $ n $ integers. Let's number the array elements from 1 to $ n $ , then the $ i $ -th element will be denoted as $ a_{i} $ . The Little Elephant can make one move to choose an arbitrary pair of integers $ l $ and $ r $ $ (1<=l<=r<=n) $ and increase $ a_{i} $ by $ 1 $ for all $ i $ such that $ l<=i<=r $ . Help the Little Elephant find the minimum number of moves he needs to convert array $ a $ to an arbitrary array sorted in the non-decreasing order. Array $ a $ , consisting of $ n $ elements, is sorted in the non-decreasing order if for any $ i $ $ (1<=i&lt;n) $ $ a_{i}<=a_{i+1} $ holds.

输入输出格式

输入格式

The first line contains a single integer $ n $ $ (1<=n<=10^{5}) $ — the size of array $ a $ . The next line contains $ n $ integers, separated by single spaces — array $ a $ $ (1<=a_{i}<=10^{9}) $ . The array elements are listed in the line in the order of their index's increasing.

输出格式

In a single line print a single integer — the answer to the problem. Please, do not use the %lld specifier to read or write 64-bit integers in С++. It is preferred to use the cin, cout streams or the %I64d specifier.

输入输出样例

输入样例 #1

3
1 2 3

输出样例 #1

0

输入样例 #2

3
3 2 1

输出样例 #2

2

输入样例 #3

4
7 4 1 47

输出样例 #3

6

说明

In the first sample the array is already sorted in the non-decreasing order, so the answer is $ 0 $ . In the second sample you need to perform two operations: first increase numbers from second to third (after that the array will be: \[3, 3, 2\]), and second increase only the last element (the array will be: \[3, 3, 3\]). In the third sample you should make at least 6 steps. The possible sequence of the operations is: (2; 3), (2; 3), (2; 3), (3; 3), (3; 3), (3; 3). After that the array converts to \[7, 7, 7, 47\].