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 C# (Mono 4.6.2.0) (judge verdict: Accepted)

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Diagnostics;

namespace PaizaSkillCheck
{
    public class Program
    {
        public static int[] flower;

        public static void Main(string[] args)
        {
            int n = int.Parse(Console.ReadLine());

            string[] line = Console.ReadLine().Split(' ');
            int[] flower = new int[n];

            int minHeight = int.MaxValue;

            for (int i = 0; i < flower.Length; i++)
            {
                int v = int.Parse(line[i]);
                flower[i] = v;

                minHeight = Math.Min(minHeight, v);
            }

            int needCount = minHeight;
            int nowHeight = minHeight;
            int endCount = 0;

            while (endCount != flower.Length)
            {
                endCount = 0;
                for (int i = 0; i < flower.Length; i++)
                {
                    if (flower[i] > nowHeight)
                    {
                        //  左端
                        if (i == 0 || flower[i - 1] <= nowHeight)
                        {
                            needCount++;
                        }
                    }
                    else
                    {
                        endCount++;
                    }
                }
                nowHeight++;
            }

            Console.WriteLine(needCount);
        }
    }
}