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)

def main():
    N = int(input())
    price = [int(input()) for i in range(N)]
    minv = float("inf")
    maxv = -float("inf")
    for p in price:
        maxv = max(maxv, p-minv)
        minv = min(minv, p)
    print(maxv)



if __name__ == "__main__":
    import os
    import sys
    if len(sys.argv) > 1:
        if sys.argv[1] == "-d":
            fd = os.open("input.txt", os.O_RDONLY)
            os.dup2(fd, sys.stdin.fileno())
            main()
    else:
        main()