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;

    class ABC116C
    {
        static void Main(string[] args)
        {
            Method(args);
        }

        static void Method(string[] args)
        {
            int n = int.Parse(Console.ReadLine());
            string[] input = Console.ReadLine().Split(' ');
            int[] h = new int[n+1];
            for(int i = 1; i <= n; i++)
            {
                h[i] = int.Parse(input[i-1]);
            }
            int l, r;
            int cnt = 0;

            // 端から攻めてく

            for(int i = 1; i <= n; i++)
            {
                 while(h[i] != 0)
                {
                    l = i;
                    r = i;
                    for(int j = i+1; j <= n; j++)
                    {
                        if(h[j] != 0)
                        {
                            r = j; // ここ念のため
                        }
                        if(h[j] == 0)
                        {
                            r = j - 1;
                            break;
                        }
                    }

                    for(int x = l; x <= r; x++)
                    {
                        h[x]--;
                    }
                    cnt++;
                }
            }

            Console.WriteLine(cnt);
        }
    }