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)

n = gets.to_i
rt = [gets.to_i]
got2 = gets.to_i
for i in 2..n-2
  got1 = gets.to_i
  if rt[-1]<got2
    if got2<=got1
      got2 = got1
    else
      rt<<got2
    end
  end
  if rt[-1]>got2
    if got2>=got1
      got2 = got1
    else
      rt<<got2
    end
  end
end
rt << gets.to_i 
l = rt.size
ans = rt[1]-rt[0]
for i in 2..l-1
  for j in i+1..l-1
    x = rt[i]-[j]
    ans = x if ans<x
  end
end
puts ans