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.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace ConsoleApp89 {
    class Program {
        static int ans = 0;

        static void Main(string[] args) {
            int N = int.Parse(Console.ReadLine());

            var h = Console.ReadLine().Split().Select(int.Parse).ToList();

            CountAndSplitList(h);

            Console.WriteLine(ans);

        }

        static void CountAndSplitList(List<int> p_) {
            if (p_.Count() == 0) {
                return;
            }

            if (p_.Distinct().Count() == 1) {
                ans += p_.Min();    
                return;
            }

            ans += p_.Min();

            var h_new = p_.Select(x => x - p_.Min()).ToList();
            var a = new List<List<int>>();
            a.Add(new List<int>());
            int index = 0;

            for (int i = 0; i < h_new.Count(); i++) {
                if (h_new[i] != 0) {
                    a[index].Add(h_new[i]);
                }
                if (i != (h_new.Count() - 1) && h_new[i] == 0 && h_new[i + 1] != 0) {
                    a.Add(new List<int>());
                    index++;
                }
            }

            foreach (var element in a) {
                CountAndSplitList(element);
            }
        }
    }
}