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: Time Limit Exceeded)

import scala.annotation.tailrec

object Main {
  def main(args: Array[String]): Unit = {
    val n = readLine.toInt
    val _input = new Array[Int](n)
    1 to n foreach { i =>
      _input(i-1) = readLine.toInt
    }
    val input = _input.toList

    println(calMaxProf(input))
  }

  @tailrec def calMaxProf(input: List[Int], maxProf: Int = Int.MinValue, last: Int = Int.MaxValue): Int = input match {
    case head :: Nil =>
      maxProf
    case head :: tail =>
      if (head < last) {
        val prof = tail.map(_ - head).max
        if (prof > maxProf) {
          calMaxProf(tail, prof, head)
        } else {
          calMaxProf(tail, maxProf, last)
        }
      } else {
        calMaxProf(tail, maxProf, last)
      }
    case Nil =>
      maxProf
  }
}