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 Java8 (OpenJDK 1.8.0) (judge verdict: Accepted)

import java.util.Scanner;

 

public class Main {

 

    public static void main(String[] args) {
        Scanner scan = new Scanner(System.in);
        int flowerNum = scan.nextInt();                        // 花の総本数
        int[] flowerHeightList = new int[flowerNum];             // 花の高さを入れる配列
        int count = 0;                                             // 水やり回数

 

        /* データ入力 */
        for (int i = 0; i < flowerNum; i++) {
            flowerHeightList[i] = scan.nextInt();
        }

 

        int tmp = 0;
        int head = 0;
        

 

        while(head < flowerNum) {
            // 先頭の高さが0だった場合、次の要素を先頭とする
            if(flowerHeightList[head] == 0) {
                tmp = ++head;
                continue;
            }
            // 水やりの範囲を決定する
            for(int tail = head; tail < flowerNum; tail++) {
                if(flowerHeightList[tail] == 0) {
                    head = tmp;
                    break;
                }
                flowerHeightList[tail]--;
            }
            count++;
        }

 

        System.out.println(count);
        scan.close();
    }

 

}