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)

n, *R = map(int, open(0).read().split())
A = [int(-1e9) for _ in range(n)]
B = [int(1e9) for _ in range(n)]
A[n-1] = max(A[n-1], R[n-1])
B[0] = min(B[0], R[0])
for i in range(n-1, 0, -1):
    A[i-1] = max(R[i-1], A[i])
for i in range(n-1):
    B[i+1] = min(B[i], R[i+1])

ans = int(-3e9)
for i in range(n-1):
    ans = max(ans, A[i+1] - B[i])
print(ans)