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;

namespace ABC116_C___Grand_Garden
{
    class Program
    {
        static int[] garden;
        static void Main(string[] args)
        {
            Console.ReadLine();
            garden = Array.ConvertAll(Console.ReadLine().Split(' '), int.Parse);
            Console.WriteLine(watering(0, garden.Length - 1, 0));
        }

        static int watering(int left, int right, int bottom)
        {
            if (left == right) return garden[left] - bottom;

            int min = int.MaxValue;
            int minIndex = 0;
            for (int i = left; i <= right; i++)
            {
                if (garden[i] < min)
                {
                    min = garden[i];
                    minIndex = i;
                }
            }

            if (minIndex == left)
            {
                return watering(left + 1, right, min) + min - bottom;
            }
            else if (minIndex == right)
            {
                return watering(left, right - 1, min) + min - bottom;
            }
            else
            {
                return watering(left, minIndex - 1, min) + watering(minIndex + 1, right, min) + min - bottom;
            }
        }
    }
}