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 max(a, b)
  if a.nil?
    b
  else
    (a > b) ? a : b
  end
end

n = gets.to_i

data = Array.new
for i in 1..n do
  data[i - 1] = gets.to_i
end

mx = nil

for i in 1..n-1 do
  for j in i + 1 .. n do
    mx = max(mx, data[j - 1] - data[i - 1])
  end
end

puts mx