Problem:
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Maximum Profit

You can obtain profits from foreign exchange margin transactions. For example, if you buy 1000 dollar at a rate of 100 yen per dollar, and sell them at a rate of 108 yen per dollar, you can obtain (108 - 100) × 1000 = 8000 yen.

Write a program which reads values of a currency $R_t$ at a certain time $t$ ($t = 0, 1, 2, ... n-1$), and reports the maximum value of $R_j - R_i$ where $j > i$ .

Input

The first line contains an integer $n$. In the following $n$ lines, $R_t$ ($t = 0, 1, 2, ... n-1$) are given in order.

Output

Print the maximum value in a line.

Constraints

$2 \leq n \leq 200,000$

$1 \leq R_t \leq 10^9$

Sample Input 1

6
5
3
1
3
4
3

Sample Output 1

3

Sample Input 2

3
4
3
2

Sample Output 2

-1

Solution in Rust (judge verdict: Accepted)

fn read<T: std::str::FromStr>() -> T {
        let mut s = String::new();
        std::io::stdin().read_line(&mut s).ok();
        s.trim().parse().ok().unwrap()
}

fn read_col<T: std::str::FromStr>(n: u32) -> Vec<T> {
        (0..n).map(|_| read()).collect()
}


fn main() {
    let n: i32 = read();
    let v: Vec<i32> = read_col(n as u32);

    let mut min = std::cmp::min(v[0], v[1]);
    let mut max = v[1] - v[0];
    let mut tmp: i32;

    for i in 2..n {
        tmp = v[i as usize] - min;
        max = std::cmp::max(tmp, max);
        min = std::cmp::min(v[i as usize], min);
    }

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