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: Memory Limit Exceeded)

import scala.collection.mutable

object Main {
  def main(args: Array[String]): Unit = {
    val n = io.StdIn.readInt()
    val r = Iterator.continually(io.StdIn.readInt()).take(n).toSeq
    val (_, mins) = r.foldLeft((Int.MaxValue, mutable.ListBuffer.empty[Int])) { case ((min, z), ri) =>
      z += min
      (Math.min(min, ri), z)
    }

    println(r.tail.zip(mins.tail).map { case (i, min) => i - min }.max)
  }
}