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;

public class Hello
{
    private const int INF = 1000000007;
    public static void Main()
    {
        int N = Input.Cin<int>();
        int[] f = Input.Line<int[]>();
        int ans = 0;
        while (true)
        {
            int c = 1;
            bool seach = true;
            bool skip = false;
            for (int i = 0; i < N; i++)
            {
                if (seach && f[i] != 0) { seach = false; skip = true; }
                if (skip && f[i] == 0)
                {
                    skip = false;
                    seach = true;
                    ans += 1;
                }
                if (skip) f[i]--;
            }
            if (skip) ans++;

            if (f.All(v => v == 0)) break;
        }
        Console.WriteLine(ans);
    }
}

public class Input
{
    private static Queue<string> queue = new Queue<string>();
    public static T Cin<T>()
    {
        if (queue.Count == 0) foreach (var s in Console.ReadLine().Split(' ')) queue.Enqueue(s);
        if (typeof(T) == typeof(int)) return (T)(object)int.Parse(queue.Dequeue());
        else if (typeof(T) == typeof(long)) return (T)(object)long.Parse(queue.Dequeue());
        else if (typeof(T) == typeof(string)) return (T)(object)(queue.Dequeue());
        else if (typeof(T) == typeof(double)) return (T)(object)double.Parse(queue.Dequeue());
        else return (T)(object)(0);
    }
    public static T Line<T>()
    {
        foreach (var s in Console.ReadLine().Split(' ')) queue.Enqueue(s);
        int c = queue.Count();
        if (typeof(T) == typeof(int[]))
        {
            int[] ret = new int[c];
            for (int i = 0; i < c; i++) ret[i] = Cin<int>();
            return (T)(object)ret;
        }
        else if (typeof(T) == typeof(long[]))
        {
            long[] ret = new long[c];
            for (int i = 0; i < c; i++) ret[i] = Cin<long>();
            return (T)(object)ret;
        }
        else if (typeof(T) == typeof(string[]))
        {
            string[] ret = new string[c];
            for (int i = 0; i < c; i++) ret[i] = Cin<string>();
            return (T)(object)ret;
        }
        else if (typeof(T) == typeof(double[]))
        {
            double[] ret = new double[c];
            for (int i = 0; i < c; i++) ret[i] = Cin<double>();
            return (T)(object)ret;
        }
        else return (T)(object)(0);
    }
}