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: Wrong Answer)

arrs = [6, 5, 3, 1, 3, 4, 3, 8, 9, 10]
t0 = Time.now
1.upto(10000).each { |v| arrs << [*-10..10].sample }
cal_i = 0
arr_size = arrs.size
max_diff_val = nil
min_val = nil
t1 = Time.now
arrs.each_with_index do |val, index|
  min_val = val if index == 0
  max_diff_val = val - min_val
  min_val = val if val < min_val
  cal_i += 1
end

t2 = Time.now
puts max_diff_val
puts min_val
puts cal_i
puts t0.strftime("%F %T")
puts t1.strftime("%F %T")
puts t2.strftime("%F %T")
puts (t2 - t1)