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 PHP (judge verdict: Accepted)

<?php

class Calculator
{
    private $N;
    private $minv;
    private $maxv;

    public function __construct()
    {
        $this->N = trim(fgets(STDIN));
        $this->minv = trim(fgets(STDIN));
        $this->maxv = 1 - 10**9;
    }

    public function ObtainMaximumProfit()
    {
        $N = $this->N;
        $minv = $this->minv;
        $maxv = $this->maxv;

        for ($i = 1; $i < $N; $i++) {
            $n = trim(fgets(STDIN));
            $profit = $n - $minv;

            if ($maxv < $profit) {
                $maxv = $profit;
            }

            if ($n < $minv) {
                $minv = $n;
            }
        }
        echo $maxv . PHP_EOL;
    }
}

$calculator = new Calculator();
$calculator->ObtainMaximumProfit();