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)

fn main() {
    let n: u32 = read();
    let reader: Box<Iterator<Item = i32>> = Box::new(ReadLines::new(n, 0));
    println!("{}", maximum_profit(reader));
}

fn maximum_profit(reader: Box<Iterator<Item = i32>>) -> i32 {
    let mut min    = i32::max_value();
    let mut profit = i32::min_value();
    for e in reader {
        let sub = e - min;
        if  sub > profit {
            profit = sub;
        }
        if e < min {
            min = e;
        }
    }
    profit
}

fn read<T: std::str::FromStr>() -> T {
    let mut input = String::new();
    std::io::stdin().read_line(&mut input).unwrap();
    input.trim().parse::<T>().ok().unwrap()
}

struct ReadLines<T: std::str::FromStr> {
    n: u32,
    cnt: u32,
    _d: T,
}
impl<T: std::str::FromStr> ReadLines<T> {
    fn new(n: u32, d: T) -> Self { ReadLines { n: n, cnt: 0, _d: d } }
}

impl<T: std::str::FromStr> Iterator for ReadLines<T> {
    type Item = T;
    fn next(&mut self) -> Option<T> {
        let ret = if self.cnt < self.n {
            let mut input = String::new();
            std::io::stdin().read_line(&mut input).unwrap();
            Some(input.trim().parse::<T>().ok().unwrap())
        } else {
            None
        };
        self.cnt += 1;
        ret
    }
}