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: Wrong Answer)

using System;
using System.Linq;

namespace train
{
	class Program
	{
		static void Main(string[] args)
		{
			int num = int.Parse( Console.ReadLine());
			string strFlowers = Console.ReadLine();
			string[] flower = strFlowers.Split(' ');
			int[] flowers = flower.Select(f => int.Parse(f)).ToArray();

			int water = 0;
			do
			{
				int min = -1;
				int max = -1;
				int lastIndex = flowers.Length -1;
				for (int n = 0; n < flowers.Length; n++)
				{
					if (min == -1)
					{
						if (flowers[n] > 0)
						{
							min = n;
							if (n == lastIndex)
								max = n;
						}
					}
					else
					{
						if (flowers[n] == 0)
							max = n - 1;
						else if (n == lastIndex)
							max = n;
					}
					if (min >= 0 && max >= min)
						break;
				}

				if(min>=0 && max >= 0)
					for (int n = min; n <= max; n++)
						flowers[n]--;

				water++;
			} while (flowers.Sum() > 0);

			Console.WriteLine(water);
		}
	}
}