Problem:
MathJax.Hub.Config({ tex2jax: { inlineMath: [["$","$"], ["\\(","\\)"]], processEscapes: true }});

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 main() {
    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()
    }

    let n = read::<u32>();

    let mut prices: Vec<i32> = Vec::new();
    for _ in 0..n {
        let mut s = String::new();
        std::io::stdin().read_line(&mut s).ok();
        let price = s.trim().parse().ok().unwrap();
        prices.push(price);
    }

    // println!("n = {}", n);
    // for p in &prices {
    //     print!("{} ", p);
    // }

    let mut r_min = prices[0];
    let mut max_profit: i32 = -2_000_000_000;
    for i in 1..prices.len() {
        max_profit = std::cmp::max(max_profit, prices[i] - r_min);
        r_min = std::cmp::min(r_min, prices[i]);
    }

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