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.stdin

object Main {
  def getMax(max:Int, min:Int, list:Iterator[Int]):Int = {
    if(list.hasNext) {
      val m = list.next()
      val (x:Int,y:Int) =
        if(max < m-min) {
          if(min > m) (m-min,m) else (m-min,min)
        }
        else {
          if(min>m) (max,m) else (max,min)
        }
      getMax(x, y, list)
    }
    else { max }
  }

  def main(args: Array[String]) = {
    val list = stdin.getLines().map { _.toInt }
    val n = list.next()
    val r0 = list.next()
    val r1 = list.next()
    val max = getMax(r1 - r0, if(r0 > r1) r1 else r0, list)

    println(max)
  }
}