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 static System.Console;
using static MyUtil;

class MyUtil
{
    public static int[] ReadIntArray()
    {
        return ReadLine().Split().Select(x => int.Parse(x)).ToArray();
    }
}

class Program
{
    public static void Main()
    {
        int n = int.Parse(ReadLine());
        var h = ReadIntArray();

        int allh = h.Sum();
        int ans = 0;
        int mode = 0;

        while (allh > 0)
        {
            for (int i = 0; i < n; i++)
            {
                if (i == 0){ mode = 0; }

                if (h[i] > 0)
                {
                    if (mode == 0){ // start new watering
                        ans++;
                    }
                    mode = 1;
                    h[i]--;
                    allh--;
                }
                else
                {
                    mode = 0;
                }
            }
        }

        WriteLine(ans);
    }
}