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: Wrong Answer)

using System;
using System.Linq;
using System.Collections.Generic;

class Procon
{
  public Procon() {}
  static void Main(string[] agrs)
  {
    new Procon().Do();
  }

  Scanner cin;

  public void Do()
  {
    cin = new Scanner();
    int N = cin.nextInt();
    int[] h = cin.arrayInt();

    int i;
    for (i=0;; i++) {
      mizuyari(h, N);
      int ok = 0;
      for (int j=0;j<N; j++) {
        if (h[j] != 0) {
          ok = 1;
        }
      }
      if (ok == 0) {
        break;
      }
    }
    Console.WriteLine(i+1);
  }

  public void mizuyari (int[] h, int N) {
    int min = 101;
    int l = 0;
    int r = N;

    for (int i=0; i<N; i++) {
      if (h[i] == 0) {
        if (min > 100) {
          l = i+1;
          continue;
        }
        r = i;
        break;
      } else if (h[i] < min) {
        min = h[i];
      }
    }

    if (min > 100) {
      return;
    }

    for (int i=l; i<r; i++) {
      h[i] = h[i] - 1;
    }
    return;
  }
}


class Scanner
{
  string[] s;
  int i;
  int max_i;

  public Scanner()
  {
    s = new string[0];
    max_i = 0;
    i = 0;
  }

  public string nextString()
  {
    if (i >= s.Length) 
    {
      s = Console.ReadLine().Split(' ');
      max_i = s.Length;
      i = 0;
      if (max_i == 0) 
      {
        return "";
      }
      return s[i++];
    } else 
    {
      return s[i++];
    }
  }

  public int nextInt()
  {
    return int.Parse(nextString());
  }


  public long nextLong()
  {
    return long.Parse(nextString());
  }

  public double nextDouble()
  {
    return double.Parse(nextString());
  }

  public string[] arrayString()
  {
    return Console.ReadLine().Split(' ');
  }

  public int[] arrayInt()
  {
    string[] str = Console.ReadLine().Split(' ');
    int[] array = new int[str.Length];
    for (int i=0; i<str.Length; i++) 
    {
      array[i] = int.Parse(str[i]);
    }
    return array;
  }

  public long[] arrayLong()
  {
    string[] str = Console.ReadLine().Split(' ');
    long[] array = new long[str.Length];
    for (int i=0; i<str.Length; i++) 
    {
      array[i] = long.Parse(str[i]);
    }
    return array;
  }

  public double[] arrayDouble()
  {
    string[] str = Console.ReadLine().Split(' ');
    double[] array = new double[str.Length];
    for (int i=0; i<str.Length; i++) 
    {
      array[i] = double.Parse(str[i]);
    }
    return array;
  }
}