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 Python3 (judge verdict: Accepted)

# range(stop)は0<=i<stopの連番リストを返す．stopは含まれない．
# 0始まりで1ずつ増加する連番なので，負の値を指定すると空になる．
# range(start, stop)はstrat<=i<stopの連番リストを返す．stopは含まれないので注意．
# stepを負にすることで逆順の連番リストを作成できる．

def MaximumProfit(val_list, N):
   maxv = -10e10
   minv = val_list[0]
   for i in range(1, N):
      maxv = max(maxv, val_list[i]-minv)
      minv = min(minv, val_list[i])
   return maxv

N = int(input())
val_list = [int(input()) for _ in range(N)] # 1つの数字をN行入力
ans = MaximumProfit(val_list, N)
print(ans)