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 JavaScript (node.js v5.12) (judge verdict: Accepted)

function main(input) {
  var n = input[0]-0;
  var h = input[1].split(" ").map(v=>v-0);
  var ans = 0;
  var start, end;
  for(start=0;start<n;){
    if(h[start]==0) {start++; continue;}
    var min = h[start];
    for(end=start;end<n;end++){
      if(h[end] == 0) break;
      min = Math.min(h[end], min);
    }
    for(var i=start;i<end;i++){
      h[i]-=min;
    }
    ans += min;
  }
  console.log(ans);
}

main(require('fs').readFileSync('/dev/stdin', 'utf8').trim().split("\n"))