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 Scala (2.11.7) (judge verdict: Accepted)

object Main {
    def main(args: Array[String]) = {
        val sc = new java.util.Scanner(System.in)
        val n = sc.nextInt
        val hs = List.fill(n)(sc.nextInt)
        val hs_max = hs.max
        var ans = 0
        var tmp = -1
        for (h <- 1 to hs_max) {
            for(i <- 0 until n) {
                if (hs(i) - h >= 0) {
                    if (tmp == -1) {
                        ans += 1
                        tmp = 1
                    }
                } else
                    tmp = -1
            }
            tmp = -1
        }
        println(ans)
    }
}