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: Time Limit Exceeded)

<?php
fscanf(STDIN, '%d', $n);
$h = array_map('intval', explode(' ', trim(fgets(STDIN))));

$ans = func($h);
echo $ans . PHP_EOL;

function func($h, $_min = 0) {
    $min = 100;
    $j = 0;
    foreach ($h as $i => $v) {
        if ($v > $_min) {
            $min = min($min, $v);
        }
        if ($v > $_min && ($h[$i + 1] ?? $_min) <= $_min) $j++;
    }
    $sum = ($min - $_min) * $j;
    if ($min === max($h)) return $sum;
    else  return $sum + func($h, $min);
}