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 PHP (7.4.4) (judge verdict: Wrong Answer)

<?php
fscanf(STDIN,"%d",$n);
$h_li = explode(" ",trim(fgets(STDIN)));
$sum = array_sum($h_li);
$c = 0;
$flag = false;
while(!$sum==0){
  for($i=0;$i<$n;$i++){
    if($h_li[$i]>0){
      $h_li[$i]--;
      $flag = true;
      $sum--;
    }
    if(($flag&&$h_li[$i]>0) || ($i==$n-1&&$h_li[$i]>0)){
      $c++;
      $flag = false;
    }
  }
}

echo $c;