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>) {
    val n = readInputLine().toInt()
    val hs = readInputLine().split(" ").map{it.toInt()}.toList()
    
    println(dfs(hs, 0))
}

fun readInputLine(): String {
    return readLine()!!
}

fun split(list: List<Int>, height: Int): List<List<Int>> {
    val ret = mutableListOf<List<Int>>()
    
    var l = -1
    var splitting = false
    
    for ((i, e) in list.withIndex()) {
        if (!splitting && e > height) {
            l = i
            splitting = true
        } else if (splitting && e == height) {
            ret.add(list.subList(l, i))
            splitting = false
        }
    }
    
    if (splitting) {
        ret.add(list.subList(l, list.size))
    }
    
    return ret
}

fun dfs(list:List<Int>, height:Int): Int {
    var ret = 0
    val splitted = split(list, height)
    
    for (l in splitted) {
        ret += dfs(l, height + 1) + 1
    }
    
    return ret
}