Problem:
Score : 300 points

Problem Statement

In a flower bed, there are N flowers, numbered 1,2,......,N. Initially, the heights of all flowers are 0.
You are given a sequence h=\{h_1,h_2,h_3,......\} as input. You would like to change the height of Flower k to h_k for all k (1 \leq k \leq N), by repeating the following "watering" operation:

Specify integers l and r. Increase the height of Flower x by 1 for all x such that l \leq x \leq r.

Find the minimum number of watering operations required to satisfy the condition.

Constraints

1 \leq N \leq 100

0 \leq h_i \leq 100

All values in input are integers.

Input

Input is given from Standard Input in the following format:

N
h_1 h_2 h_3 ...... h_N

Output

Print the minimum number of watering operations required to satisfy the condition.

Sample Input 1

4
1 2 2 1

Sample Output 1

2

The minimum number of watering operations required is 2.
One way to achieve it is:

Perform the operation with (l,r)=(1,3).

Perform the operation with (l,r)=(2,4).

Sample Input 2

5
3 1 2 3 1

Sample Output 2

5

Sample Input 3

8
4 23 75 0 23 96 50 100

Sample Output 3

221

Solution in Kotlin (1.0.0) (judge verdict: Accepted)

fun main(args: Array<String>) {
    abc116c()
}

fun abc116c() {
    // 愚直にやってみる 全体が1以上だったらその分引いて、1以上のところで左右に分割、それを再帰的に処理
    val n = readLine()!!.toInt()
    val heights = readLine()!!.split(" ").map { it.toInt() }
    
    println(calc(heights))
}

fun calc(heights: List<Int>): Int {
    if (heights.isEmpty()) return 0

    val max = heights.max()!!
    val min = heights.min()!!

    if (max == 0) return 0
    if (max == min) return max

    val remains = heights.map { it - min }

    val left = remains.subList(0, remains.indexOf(0))
    val right = remains.subList(remains.indexOf(0) + 1, remains.size)

    return calc(left) + calc(right) + min

}