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: Time Limit Exceeded)

using System;
using System.Collections.Generic;
using System.Linq;
 
static class MainClass {
 
  public struct City{
    public long num;
    public City(long n){
      num = n;
    }
 
  }
 
  public static void Main (string[] args) {
    var N = long.Parse(Console.ReadLine());
    var list = Console.ReadLine().Split(' ').Select(long.Parse);
    var ans = 0;

    IEnumerable<long> l = new List<long>();

    while(list.Any()){
      var zero = list.ToList().IndexOf(0);
      zero = zero == -1 ? list.Count() : zero;
      l = list.Take(zero);
      if(!l.Any()){
        list = list.Skip(1);
      }else{
        var min = l.Min();
        ans += (int)min;
        l = l.Select(x => x - min);
        list = l.Concat(list.Skip(zero));
      }
    }

    Console.WriteLine(ans);
  }

}