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::io::{Read};
use std::str::FromStr;

struct Scanner<R: Read> {
    r: R
}

impl<R: Read> Scanner<R> {
    fn new(r: R) -> Scanner<R> {
        Scanner{
            r: r,
        }
    }

    fn next<T>(&mut self) -> T
    where
    T: FromStr,
      <T as ::std::str::FromStr>::Err: ::std::fmt::Debug,
    {
        self.r.by_ref()
            .bytes()
            .map(|r: ::std::io::Result<u8>| -> u8 { r.unwrap() })
            .map(|u: u8| -> char { u as char})
            .skip_while(|c: &char| -> bool { c.is_whitespace() })
            .take_while(|c: &char| -> bool { !c.is_whitespace()})
            .collect::<String>()
            .parse::<T>()
            .unwrap()
    }
}

use std::cmp::max;

fn main() {
    let stdin = std::io::stdin();
    let mut sc = Scanner::new(stdin);

    let n: i32 = sc.next();
    let v: Vec<i32> = (0..n).map(|_| sc.next()).collect();
    let mut mv: i32 = std::i32::MIN;
    let mut buy_min: i32 = std::i32::MAX;

    for i in 0..n-1 {
        if v[i as usize] < buy_min {
            buy_min = v[i as usize]
        } else {
            continue;
        }

        for j in i+1..n {
            mv = max(mv, v[j as usize] - v[i as usize])
        }
    }
    println!("{}", mv);
}