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++14 (GCC 5.4.1) (judge verdict: Accepted)

#include <bits/stdc++.h>
using namespace std;
#define rep(i, n) for (int i = 0; i < (int)(n); i++)

int main()
{
  int N;
  cin >> N;
  vector<int> h(N);
  rep(i, N)
  {
    cin >> h[i];
  }
  int shower_count = 0;
  bool is_showering = false;

  rep(i, 100)
  {
    rep(j, N)
    {
      if (i + 1 > h[j])
      { //水を上げない
        if (is_showering)
        {
          is_showering = false;
          shower_count++;
        }

        continue;
      }

      if (is_showering)
        continue;
      else
      {
        is_showering = true;
      }
    }
    if (is_showering)
    {
      shower_count++;
      is_showering = false;
    }
  }

  cout << shower_count << endl;

  return 0;
}