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)


use std::io::{self, BufRead};

fn ff(vec:&mut Vec<i64>) -> i64 {
    let mut min = vec[0];
    let mut rv = vec[1] - vec[0];

    for n in 1 .. vec.len() {
        if rv < vec[n] - min {
            rv = vec[n] - min;
        }
        if vec[n] < min {
            min = vec[n]
        }

    }

    rv
}

fn main() {
    let mut s = String::new();
    let stdin = io::stdin();

    let _ = stdin.read_line(&mut s);
    let n:usize = s.trim().parse().unwrap();

    s.clear();

    // let nums:Vec<i64> = stdin.lock()
    //     .lines()
    //     .take(n)
    //     .map(|s| s.ok().unwrap().trim().parse().unwrap_or(0))
    //     .collect();

    let mut nums:Vec<i64> = Vec::new();

    for _ in 0 .. n {
        let _ = stdin.read_line(&mut s);
        //println!("{}", s.trim());
        nums.push(s.trim().parse().unwrap());
        s.clear();
    }

    println!("{}", ff(&mut nums));
}