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
import scala.annotation.tailrec

object Main{
  def main(args: Array[String]){
    val lines = for{
      in <- Source.stdin.getLines.toVector
    }yield in.toInt

    println(rec(lines.tail, Int.MinValue, Int.MaxValue))
  }

  @tailrec
  def rec(vec: Vector[Int], preMax: Int, preMin: Int): Int ={
    if(vec.length == 1) preMax
    else rec(vec.tail, Math.max(vec.tail.head - Math.min(preMin, vec.head), preMax), Math.min(preMin, Math.min(preMin, vec.head)))
  }
}