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::*;
use std::str::*;
use std::cmp;

fn read<T: FromStr>(s: &mut StdinLock) -> Option<T> {
    let s = s.by_ref().bytes().map(|c| c.unwrap() as char)
        .skip_while(|c| c.is_whitespace())
        .take_while(|c| !c.is_whitespace())
        .collect::<String>();
    s.parse::<T>().ok()
}

fn main() {
    let mut inputs = [0; 200000];
    
    let s = stdin();
    let mut s = s.lock();
    let s = &mut s;
    let mut num = 0;
    if let Some(n) = read(s) {
        num = n;
    }
    for i in 0..num {
        if let Some(n) = read(s) {
            inputs[i] = n;
        }
    }
    
    let mut max_diff = -2000000000;
    let mut min = &inputs[0];

    for input in &inputs[1..num] {
        max_diff = cmp::max(max_diff, *input - min);
        min = cmp::min(min, input);
    }

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