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.Diagnostics;
using System.Linq;

namespace ConsoleApp1
{
    using static Util;

    internal class Program
    {


        static void Main(string[] args)
        {
            var n = ReadLong();
            var hs = ReadLongs();
          

            var cnt = Count(hs);
            Console.WriteLine(cnt);
#if DEBUG
            Console.Read();
#endif
        }

        private static long Count(long[] h)
        {
            h = h.ToArray();
            var res = 0;
            while (true)
            {
                if (h.Max() == 0) break;
                // 区間分割する
                int i = 0;
                while (i < h.Length)
                {
                    if (h[i] == 0) ++i; // 0 なら何もせずに次に進む
                    else
                    {
                        ++res; // 区間の始まり
                        while (i < h.Length && h[i] > 0)
                        {
                            --h[i];
                            ++i; // 区間の終わりまで一気に
                        }
                    }
                }
            }
            return res;
        }

        public static long fn(long n)
        {
            if (n % 2 == 0)
                return f1(n);
            else
                return f2(n);
        }

        public static long f1(long n)
        {
            return n / 2;
        }

        public static long f2(long n)
        {
            return 3*n +1;
        }

    }

    public static class Util
    {
        public static long[] ReadLongs() 
        {
            return Console.ReadLine().Split(' ').Select(x => long.Parse(x)).ToArray();
        }
        public static long ReadLong()
        {
            return long.Parse(Console.ReadLine());
        }

        public static Tuple<int, long> FindMin(this IEnumerable<long> vals)
        {
            var min = long.MaxValue;
            var minIdx = 0;
            var cnt = 0;
            foreach(var val in vals)
            {
                if (min > val)
                {
                    min = val;
                    minIdx = cnt;
                }
                cnt++;
            }
            return Tuple.Create(cnt, min);
        }

    }
}