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 Scala (judge verdict: Accepted)

import scala.io.Source

object Main {
//  def calcMaxProfit(numbers: Seq[Int]): Int = {
//    val maxProfit: Int = (1 to numbers.size-1)
//      .toStream
//      .map{i =>
//        val a  = numbers(i-1)
//        val bs = numbers.toStream.drop(i)
//        bs.max - a
//      }
//      .max
//    maxProfit
//  }

  def calcMaxProfit(numbers: Seq[Int]): Int = {
    var min       = numbers(0)
    var maxProfit = numbers(1) - min
    for(i <- 1 until numbers.size) {
      maxProfit = math.max(maxProfit, numbers(i) - min)
      min       = math.min(min, numbers(i))
    }
    maxProfit
  }


  def main(args: Array[String]): Unit = {
    // Get interator of stdin
    val stdinIterator = Source.stdin.getLines()

    // Skip the first line
    stdinIterator.next()

    // Get input
    val numbers: Seq[Int] = stdinIterator.toSeq.map(_.toInt).toArray

    // Calc max profit
    val maxProfit = calcMaxProfit(numbers)

    // Print max profit
    println(maxProfit)
  }
}