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.*;

import static java.lang.System.*;

public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int N = sc.nextInt();

        int ans = 0;
        int count = 0;  //水やり完了済
        boolean watered = false;

        int[] h = new int[N];
        for (int i = 0; i < N; i++) {
            h[i] = sc.nextInt();
            if (h[i] == 0) {
                count++;
            }
        }

        while (count < h.length) {
            for (int i = 0; i < N; i++) {
                // 0でなければ減らす
                if (h[i] > 0) {
                    h[i]--;
                    if (h[i] == 0) {
                        count++;
                    }
                    watered = true;
                    continue;
                }

                // 0になってたら別の水やり操作が必要
                if (watered) {
                    ans++;
                    watered = false;
                }
            }

            if (watered) {
                ans++;
                watered = false;
            }
        }

        out.println(ans);
    }
}