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Given an array of positive integers `target`

and an array `initial`

of same size with all zeros.

Return the minimum number of operations to form a `target`

array from `initial`

if you are allowed to do the following operation:

- Choose
**any**subarray from`initial`

and increment each value by one.

**Example 1:**

Input:target = [1,2,3,2,1]Output:3Explanation:We need at least 3 operations to form the target array from the initial array. [0,0,0,0,0] increment 1 from index 0 to 4 (inclusive). [1,1,1,1,1] increment 1 from index 1 to 3 (inclusive). [1,2,2,2,1] increment 1 at index 2. [1,2,3,2,1] target array is formed.

**Example 2:**

Input:target = [3,1,1,2]Output:4Explanation:(initial)[0,0,0,0] -> [1,1,1,1] -> [1,1,1,2] -> [2,1,1,2] -> [3,1,1,2] (target).

**Example 3:**

Input:target = [3,1,5,4,2]Output:7Explanation:(initial)[0,0,0,0,0] -> [1,1,1,1,1] -> [2,1,1,1,1] -> [3,1,1,1,1] -> [3,1,2,2,2] -> [3,1,3,3,2] -> [3,1,4,4,2] -> [3,1,5,4,2] (target).

**Example 4:**

Input:target = [1,1,1,1]Output:1

**Constraints:**

`1 <= target.length <= 10^5`

`1 <= target[i] <= 10^5`