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.Arrays;
import java.util.Comparator;
import java.util.List;
import java.util.Scanner;
import java.util.stream.Collectors;

public class Main {

    private static Scanner scanner = new Scanner(System.in);

    public static void main(String[] args) {
        int N = scanner.nextInt();
        int[] h = new int[N];
        for (int i = 0; i < N; i++) h[i] = scanner.nextInt();
        List<Integer> hList = Arrays.stream(h).boxed().sorted(Comparator.reverseOrder()).collect(Collectors.toList());

        int max = hList.get(0);

        int count = 0;
        int[] flowers = h;
        for (int i = 0; i < max; i++) {
            StringBuilder builder = new StringBuilder();
            for (int flower : flowers) builder.append(flower > 0 ? String.valueOf(flower).replace("0", "A") : flower);
            count += Arrays.stream(builder.toString().split("0")).filter(s -> !s.trim().equals("")).count();

            for (int j = 0; j < N; j++) {
                if (flowers[j] > 0) flowers[j]--;
            }
        }

        System.out.println(count);
    }

}