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 Java (OpenJDK 11.0.6) (judge verdict: Accepted)

import java.util.ArrayList;
import java.util.Arrays;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Map.Entry;
import java.util.Scanner;

public class Main{



	public static void main(String[] args) {

		Scanner scanner = new Scanner(System.in);

		int n        = Integer.parseInt(scanner.nextLine());
		String[] tmp = scanner.nextLine().split(" ");
		int[] list   = new int[n];
		int ans    	 = 0;

		for(int i = 0; i < n; i++) {
			list[i] = Integer.parseInt(tmp[i]);
		}


		for(int i = 0; i < n; i++) {

			int r   = i;
			int min = Integer.MAX_VALUE;

			while(list[i] != 0) {
				while(r < n && list[r] != 0) {

					min = Math.min(min, list[r]);
					r++;
				}

				for(int k = i; k < r; k++) {

					list[k] -= min;
				}

				ans += min;
				r = i;
			}

		}

		System.out.println(ans);
	}
}