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)

use std::cmp::{max, min};
use std::io::stdin;
use std::str::FromStr;

fn main() {
    let n: usize = input().unwrap();
    let h: Vec<i32> = input_vec().unwrap();

    let mut ans = h[0];
    for i in 0..n-1 {
        if h[i+1] > h[i] {
            ans += h[i+1] - h[i];
        }
    }

    println!("{}", ans);
}

fn input<T: FromStr>() -> Result<T, T::Err> {
    let mut buf = String::new();
    stdin().read_line(&mut buf).unwrap();
    Ok(buf.trim().parse().ok().unwrap())
}

fn input_vec<T: FromStr>() -> Result<Vec<T>, T::Err> {
    let mut buf = String::new();
    stdin().read_line(&mut buf).unwrap();
    Ok(buf
        .trim()
        .split_whitespace()
        .map(|x| x.parse().ok().unwrap())
        .collect::<Vec<_>>())
}

fn input_two<T: FromStr>() -> Result<(T, T), T::Err> {
    let tmp = input_vec::<String>().unwrap();
    Ok((tmp[0].parse()?, tmp[1].parse()?))
}

fn input_three<T: FromStr + Clone>() -> Result<(T, T, T), T::Err> {
    let tmp = input_vec::<T>().ok().unwrap();
    // println!("{:?}", tmp);
    Ok((tmp[0].clone(), tmp[1].clone(), tmp[2].clone()))
}