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: Time Limit Exceeded)

using System;
using System.Collections.Generic;
using System.Linq;

namespace CSharpSample01
{
    
    class Program
    {

        
        static void Main(string[] args) 
        {
            int N = int.Parse(Console.ReadLine());
            int[] h = Console.ReadLine().Split(' ').Select(x => int.Parse(x)).ToArray();          

            int r = 0;
            int l = 0;
            long cnt = 0;
            while (true)
            {
                //l見つける
                for(int i = 0; i < h.Length; i++)
                {                   
                    if(h[i] != 0)
                    {
                        l = i;
                        break;
                    }
                    
                    if(i == h.Length - 1)
                    {
                        Console.WriteLine(cnt);
                        return;
                    }                    
                }

                //r見つける
                for(int i = l; i < h.Length; i++)
                {

                    if (i >= h.Length - 1)
                    {
                        r = i;
                        break;
                    }

                    if (h[i] == 0)
                    {
                        r = i - 1;
                        break;
                    }

                    
                }

                //位置ずつ消す
                for(int i = l; i <= r; i++)
                {
                    h[i]--;
                }

                cnt++;

                /*
                Console.WriteLine($"l = {l} r = {r}");

                Console.WriteLine(string.Join(" ", h));
                Console.ReadLine();
                */

            }

        }
    }
}