Problem:
MathJax.Hub.Config({ tex2jax: { inlineMath: [["$","$"], ["\\(","\\)"]], processEscapes: true }});

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: Runtime Error)

gets
r = readlines.map(&:to_i)
min = r[0..-2].min
max = r[1..-1].max
pf = []

while ((r[1..-1].index(max) + 1) < r[0..-2].index(min))
  pf<<r.slice!(r.index(min)..-1).map{|i| i - min}.max
  pf<<r.slice!(0..r.index(max)).map{|i| max - i}.max
  min = r[0..-2].min
  max = r[1..-1].max
end
pf<<(max-min)
p pf.max