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.Linq;
using System.Collections.Generic;
using System.Text;
using static System.Console;
using static System.Math;

class Program
{
    static void Main(string[] args)
    {
        int N = ReadLineParseInt();
        int[] h = ReadLineParseIntArray();
        int ans = 0;
        int l = 0;
        int r = N;
        int max = -1;
        while (max != 0)
        {
            bool flag = false;
            max = 0;
            for(int i = 0; i < N; i++)
            {
                if (!flag && h[i] != 0)
                {
                    flag = true;
                    l = i;
                }
                else if (flag && h[i] == 0)
                {
                    r = i;
                    break;
                }
            }
            for(int i = l; i < r; i++)
                h[i]--;
            ans++;
            l = 0;
            r = N;
            max = h.Max();
        }
        WriteLine(ans);
    }

    static int ReadLineParseInt() => int.Parse(ReadLine());
    static int[] ReadLineParseIntArray() => ReadLine().Split(' ').Select(int.Parse).ToArray();
}