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 search(h) {
    var is_start = false;
    for (var i = 0; i < h.length; i++) {
        if (is_start) {
            if (h[i] == 0) {
                break
            }
            h[i] -= 1

        } else {
            if (h[i] == 0) {
                continue;
            }

            is_start = true;
            h[i] -= 1
        }
    }
    return h
}

function main(arg) {
	var h = arg.split("\n")[1].split(" ").map(e => Number(e))
	var arr = []

	// 0対策
	if (h[0] == 0) {
		var b = h.filter((x, i, self) => self.indexOf(x) === i);
		if (b.length == 1) {
			console.log(0)
			return
		}
	}

    var i = 0;

    for (i = 1;;i++) {
        h = search(h)
        if (h[0] == 0) {
            var b = h.filter((x, i, self) => self.indexOf(x) === i);
            if (b.length == 1) {
                break
            }
        }
    }
	 console.log(i)
}
main(require('fs').readFileSync('/dev/stdin', 'utf8'));