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));
$map = explode(" ", trim(fgets(STDIN)));
$count = 0;
while(max($map) > 0){
    $max = max($map);
    $maxPosition = array_search($max, $map);
    $map[$maxPosition]--;
    $r = $maxPosition + 1;
    $l = $maxPosition - 1;
    while(isset($map[$r]) && $map[$r] > 0){
        $map[$r]--;
        $r++;
    }
    while(isset($map[$l]) && $map[$l] > 0){
        $map[$l]--;
        $l--;
    }
    $count++;
}
echo $count;