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::*;

fn main() {
    let stdin = stdin();
    let mut lines = stdin.lock().lines().map(|l| l.unwrap());

    let n: usize = lines.next().unwrap().parse().unwrap();
    let mut nums = lines.take(n).map(|s| s.parse::<i32>().unwrap());

    let mut answer: i32 = 0_i32;
    let mut min_val: i32 = 0_i32;
    
    for (index, val) in nums.enumerate() {
        if index != 0 && (index == 1 || answer < val - min_val) {
            answer = val - min_val;
        }
        if index == 0 || val < min_val {
            min_val = val;
        }
    }

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