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;


public class C
{
	public static void Main()
	{
		int N = Int32.Parse(Console.ReadLine());
		int[] r = new int[N + 2];
		r[N + 1] = 0;  // sentinel
		
		string[] args = Console.ReadLine().Split(' ');

		int hMax = 0;
		for(int i = 0; i < N; i++)
		{
			int h = Int32.Parse(args[i]);
			if(h > hMax)
				hMax = h;
			r[i + 1] = h;	
		}
		
		int counter = 0;
		for(int i = 1; i <= hMax; i++)
		{
			for(int j = 1; j <= N; j++)
			{	
				if(r[j] > 0)
				{
					counter++;
					do
					{
						r[j]--;
						j++;
					}
					while(r[j] > 0);
				}
			}			
		}
		
		Console.WriteLine(counter);
	}
}