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 Haskell (judge verdict: Accepted)

import Control.Monad
import Control.Applicative
import Debug.Trace

main :: IO ()
main = do
  n <- readLn :: IO Int
  ns <- replicateM n readLn :: IO [Int]
  print $ solve ns

solve :: [Int] -> Int
solve (n:ns:nss) = go (min n ns) (ns - n) nss
  where
    go x y [] = y
    go x y (z:zs)
      | z < x = go z y zs
      | y < z - x = go x (z-x) zs
      | otherwise = go x y zs
--solve [n, m] = m - n