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 AtC
{
    class Program
    {
        static void Main(string[] args)
        {
            var N = int.Parse(Console.ReadLine());
            var h = Console.ReadLine().Split(' ').Select(int.Parse).ToArray();
            Console.WriteLine(Count(h, 0, N));
        }

        static int Count(int[] arr, int start, int end)
        {
            if (end <= start) return 0;
            int min = int.MaxValue;
            for (int i = start; i < end; i++)
                if (arr[i] < min)
                    min = arr[i];
            for (int i = start; i < end; i++) arr[i] -= min;
            int count = min;
            int indexBuf = start;
            for (int i = start; i <= end; i++)
            {
                if (i == end || arr[i] == 0)
                {
                    count += Count(arr, indexBuf, i);
                    indexBuf = i + 1;
                }
            }

            return count;
        }
    }
}