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)

"use strict";

function main(input) {
  const inputs = input.split("\n").filter(x => x !== "");

  let N = Number(inputs[0]);
  let h = inputs[1].split(" ").map(Number);

  console.log(mizuyari(h))

}

function mizuyari(h) {
  // console.log(h);
  let totalCount = 0;
  let count = Math.min(...h);
  totalCount += count;

  let afterH = h.map(x => x - count);

  let subH = [];
  for(let i=0; i<afterH.length; i++) {
    if (afterH[i] !== 0) {
      subH.push(afterH[i]);
    } else {
      if (subH.length > 0) {
        totalCount += mizuyari(subH);
        subH = [];
      }
    }
  }

  if (subH.length > 0) {
    totalCount += mizuyari(subH);
    subH = [];
  }

  // console.log(totalCount);
  return totalCount; 
}

main(require("fs").readFileSync("/dev/stdin", "utf8"));