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 PHP7 (7.0.15) (judge verdict: Accepted)

<?php
  $n=trim(fgets(STDIN));
  $h = explode(" ", trim(fgets(STDIN)));

  $count = 0;
  while(array_sum($h) < (101*$n)){
      $min = min($h);
      $flag = false;
      for($j=0; $j<$n; $j++){
          if($h[$j] >= $min && $h[$j] != 101){
              $flag=true;
              $h[$j] -= $min;
          }else{
              if($flag){
                  $count += $min;
              }
              $flag = false;
          }
          if($h[$j] == 0) $h[$j] = 101;
      }
      if($flag) $count+=$min;
  }
  echo $count;