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)

def find_the_remainder(p)
  length = p.length
  output = []
  minv = 20000000000001
  for i in 0..(length-2)
    for j in 0..(length-1)
      next if  j<= i || minv < p[i]
      minv = p[i]
      result = (p[j]) - (p[i])
      if output.include?(result)
        next
      else
        output.push(result)
      end
    end
  end
  return output
end

# def find_the_remainder(p)
#   length = p.length
#   maxv = 20000000000001
#   minv = -2000000000001
#   for i in 0..(length-1)
#     if maxv <
# end
n = gets.chomp.to_i
input_values = []
n.times do
  input_value = gets.chomp.to_i
  input_values.push(input_value)
end

puts find_the_remainder(input_values).max