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;

namespace algorithm
{
	class Program
	{
		public static void Main()
		{
			int[] q = Array.ConvertAll(Console.ReadLine().Split(), int.Parse);
			int[] work = new int[q[0]];
			int[] q2 = Array.ConvertAll(Console.ReadLine().Split(), int.Parse);
			int ans = 0;
			List<int> tmp = new List<int>();
			int start = -1;
			int min = 100;
			while (true)
			{
				if (work.Sum() == q2.Sum()) break;
				//全ての配列に処理を行う
				for (int i = 0; i < work.Length; i++)
				{
					if (q2[i] == work[i])
					{
						if (start != -1)
						{
							//既定範囲に加算処理
							for (int j = start; j < i; j++)
							{
								work[j] += 1;
							}
							ans++;
							//初期化
							start = -1;
						}
						
					}
					else
					{
						//開始位置
						if (start == -1 ) start = i;
					}
				}
				//全探索
				if (start != -1)
				{
					for (int i = start; i < work.Length; i++)
					{
						work[i]++;
					}
					ans++;
					start = -1;
				}
			}

			Console.WriteLine(ans);




		}
	}

}