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)

n = gets.to_i
rs = []
n.times do
  rs << gets.to_i
end

max = -10 ** 9
min = rs[0]
rs.length.times do |i|
  break if i == rs.length - 1
  next if rs[i] > min
  min = rs[i]
  (i+1..rs.length-1).each do |j|
    max = rs[j] - rs[i] if rs[j] - rs[i] > max
  end
end

puts max