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::i32;

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

    // N
    stdin.read_line(&mut buf).unwrap();
    let n: usize = buf.trim().parse().unwrap();

    let mut r: Vec<i32> = vec![0; n];
    for i in 0..n {
        let mut buf = String::new();
        stdin.read_line(&mut buf).unwrap();
        r[i] = buf.trim().parse().unwrap();
    }

    let mut minv = r[0];
    let mut maxdf = i32::MIN;
    for i in 1..n {
        if maxdf < r[i] - minv {
            maxdf = r[i] - minv;
        }
        if r[i] < minv { 
            minv = r[i];
        }
    }

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