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;
class Program
{
    static void Main(string[] args)
    {
            // 入力
            string s2 = System.Console.ReadLine().Trim();
            int iN = int.Parse(s2);
            string[] sS = System.Console.ReadLine().Trim().Split(' ');
            List<int> lstFlw = new List<int>();
            for (int i = 0; i < sS.Length; i++)
            {
                lstFlw.Add(int.Parse(sS[i]));                   // 規定の高さ
            }

            System.Diagnostics.Stopwatch sw = new System.Diagnostics.Stopwatch();
            sw.Start();

            // 解析
            int iC = 0;                                         // 水やり回数
            while (true)
            {
                Boolean bWat = false;                           // 水やり中
                Boolean bOne = false;                           // 1回でも水やりやったか？
                for (int i = 0; i < lstFlw.Count; i++)          // 全ての花に対して
                {
                    if (lstFlw[i] == 0)                         // 規定の高さになった
                    {
                        bWat = false;                           // 水やり中止
                    }
                    else                                        // まだ成長中
                    {
                        lstFlw[i] -= 1;                         // 伸びた
                        bOne = true;                            // 1回でも水やり実施
                        if (!bWat) { iC += 1; bWat = true; }    // 水やり開始 水やり中はカウントしない
                    }
                }
                if (!bOne) { break; }                           // 1回も水やりしていない→全ての花が規定高さになった
            }

            // 出力
            System.Console.WriteLine("{0}", iC.ToString());

            sw.Stop();
#if DEBUG
            Console.WriteLine();
            Console.WriteLine("{0}", sw.Elapsed.ToString());
            Console.WriteLine("続行するには何かキーを押してください．．．");
            Console.ReadKey();
#endif
    }

}