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 Ruby (judge verdict: Time Limit Exceeded)

#!/usr/bin/env ruby

size = nil
input = []
while line = gets
  if size == nil
    size = line
  else
    input << line.chomp!.to_i
  end
end
tmp = -100000000000000000

input.each_with_index { |x, i|
  (i+1).upto(input.size-1) do |j|
    if input[j] - input[i] > tmp
      tmp = input[j]-input[i]
    end
  end
}

p tmp