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 JavaScript (judge verdict: Time Limit Exceeded)

const config = {
    input: '/dev/stdin',
    newline: '\n'
};

const line = require('fs').readFileSync(config.input, 'utf-8').split(config.newline);
const list = line.slice(1).map(x => parseInt(x));

const ans = list.reduce((acc, x, i, arr) => {
    const xs = arr.slice(i+1);
    if (xs.length > 0) {
        const max = xs.map(y => y - x).reduce((a, y) => a < y ? y : a);
        return acc < max ? max : acc;
    } else {
        return acc;
    }
}, -Infinity);

console.log(ans);