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 max_sub = i32::min_value();
  let mut min_a = nums.next().unwrap();

  for b in nums {
    if b - min_a > max_sub {
      max_sub = b - min_a;
    }
    if b < min_a {
      min_a = b;
    }
  }

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