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)

#![allow(dead_code)]
use std::io;

fn main() {
    solve_d();
}

fn solve_d() {
    let mut n = String::new();
    io::stdin().read_line(&mut n).unwrap();
    let n = n.trim().parse::<usize>().unwrap();

    let mut min = 0;
    //let mut max = 1;
    let mut already = 0;
    let mut diff = i64::min_value();
    let mut vv = vec![0; n];
    for i in 0..n {
        let mut v = String::new();
        io::stdin().read_line(&mut v).unwrap();
        vv[i] = v.trim().parse::<i64>().unwrap();

        if 1 < i {
            for j in already..i {
                //println!("already: {:?}, j: {}, i: {}", already, j, i);
                if vv[j] < vv[min] {
                    min = j;
                    //println!("min: {:?}", min);
                }
            }
            already = i - 1;
        }
        if 0 < i {
            let diff_tmp = vv[i] as i64 - vv[min] as i64;
            //println!("diff_tmp: {:?}, i: {}, min: {}", diff_tmp, i, min);
            if diff < diff_tmp {
                diff = diff_tmp
            }
        }

        /*
        for j in min..max {
            let new_diff = vv[max] as i64 - vv[j] as i64;
            if diff < new_diff {
                diff = new_diff;
                min = j;
            }
        }
        */
        //println!("min: {:?}, max: {:?}, diff_tmp: {:?}", min, max, diff_tmp);
    }
    println!("{}", diff);
}