Little Elephant and Sorting

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262144K

Description:

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 < n) a_i ≤ a_i + 1 holds.

Input:

The first line contains a single integer n (1 ≤ n ≤ 10⁵) — the size of array a. The next line contains n integers, separated by single spaces — array a (1 ≤ a_i ≤ 10⁹). The array elements are listed in the line in the order of their index's increasing.

Output:

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.

Sample Input:

3
1 2 3

Sample Output:

Sample Input:

3
3 2 1

Sample Output:

Sample Input:

4
7 4 1 47

Sample Output:

Note:

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].

Informação

Provedor Codeforces

Código CF205B