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.Linq;
using System.Collections.Generic;

class Cmondai {
    static void Main()
    {
        var num=Int32.Parse(Console.ReadLine());
        var line = Console.ReadLine().Split(' ').Select(x => Int32.Parse(x)).ToArray();
        var narabi = line.OrderByDescending(x => x).Distinct().ToList();
        narabi.Add(0);
        var maxNarabiIndex = narabi.Count() - 1;
        var ans = 0;
        for (var i=0;i<maxNarabiIndex; ++i)
        {
            var count = 1;
            var prevIndex = -1;
            for (var j=0;j<num;++j)
            {
                if (narabi[i] <= line[j])
                {
                    line[j] = narabi[i + 1];
                    if (prevIndex!=-1 && prevIndex != j - 1)
                    {
                        count++;
                    }
                    prevIndex = j;
                }
            }
            ans += (narabi[i] - narabi[i + 1]) * count;
        }
        Console.WriteLine(ans);
    }
}