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;
using System.Text;
using System.Threading.Tasks;

namespace Practice
{
    class Program
    {
        static void Main(string[] args)
        {
            int n = int.Parse(Console.ReadLine());

            int[] h = new int[n];
            string[] s = Console.ReadLine().Split(' ');
            for(int i = 0; i < n; i++)
            {
                h[i] = int.Parse(s[i]);
            }

            int count = 0;

            int k = 0;


            while (k<n)
            {
                while (h[k] == 0)
                {
                    k++;
                    if (k == n){break;}
                }
                if (k == n) { break; }

                int min = h[k];
                for (int i = k; i < n; i++)
                {
                    if (h[i] <= 0)      //途中で０にあたったとき
                    {
                        count += min;
                        for (int j = k; j < i; j++)
                        {
                            h[j] -= min;
                        }
                        break;
                    }
                    else if (h[i] < min)
                    {
                        min = h[i];
                    }else if(i == n - 1)
                    {
                        count += min;

                        for (int j = k; j < n; j++)
                        {
                            h[j] -= min;
                        }
                    }
                }
            }

            Console.WriteLine(count);


        }
    }
}