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 Rust (1.15.1) (judge verdict: Accepted)

fn main() {
    let mut s = String::new();
    std::io::stdin().read_line(&mut s).unwrap();
    let n: usize = s.trim_right().to_owned().parse().unwrap();

    let mut s = String::new();
    std::io::stdin().read_line(&mut s).unwrap();
    let s = s.split_whitespace();
    let mut hs: Vec<u32> = Vec::new();
    for h in s {
        hs.push(h.parse().unwrap());
    }
    let hmax: usize = *hs.iter().max().unwrap() as usize;
    let mut cluster_num = vec![0; hmax + 1];

    for num in 1..(hmax + 1) {
        let mut valey_flg = true;
        for i in 0..n {
            if hs[i] >= num as u32 && valey_flg == true {
                cluster_num[num] += 1;
                valey_flg = false;
            } else if hs[i] < num as u32 {
                valey_flg = true;
            }
        }
    }
    let total: u32 = cluster_num.iter().sum();
    println!("{}", total);
}