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.Linq;

namespace CSharp
{
	class Program
	{
		static void Main(string[] args)
		{
			// var N = 5;
			// var H = new int[] { 3, 1, 2, 3, 1 };
			// //             5
			// // 3 1 2 3 1
			// // 1 2 2 1

			var N = Console.ReadLine().Split().Select(int.Parse).ToArray()[0];
			var H = Console.ReadLine().Split().Select(int.Parse).ToArray();
			var res = 0;
			while (true)
			{
				if (H.Max() <= 0) break;

				var i = 0;
				res++;
				while (i < N)
				{
					if (H[i] == 0)
					{
						i++;
					}
					else
					{
						break;
					}
				}

				while (i < N && H[i] != 0)
				{
					H[i]--;
					i++;
				}
			}
			Console.WriteLine(res);
		}
	}
}