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)

use std::str::FromStr;

fn scan() -> i64 {
    let mut s = String::new();
    std::io::stdin().read_line(&mut s).unwrap();
    let mut it = s.split_whitespace().map(|n| i64::from_str(n).unwrap());
    let n = it.next().unwrap();
    n
}

fn main() {
    let mut r: Vec<i64> = Vec::new();

    let n: i64 = scan();
    for _ in 0..n {
        let v = scan();
        r.push(v);
    }
    
    let mut maxv: i64 = std::i64::MIN;
    let mut minv: i64 = r[0];
    
    for _i in 1..n {
        let i = _i as usize;
        if maxv < r[i] - minv {
            maxv = r[i] - minv;
        }
        if minv > r[i] {
            minv = r[i];
        }
    }
    
    println!("{}", maxv);
}