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 Python (judge verdict: Accepted)

#! /usr/bin/env python

def proc_inputs ():
    num_inputs = int(input())
    inputs = [int(input()) for i in range(num_inputs)]
    return inputs

def main ():
    inputs = proc_inputs()
    print(calc_prof(inputs))
    exit(0)

def calc_prof (inputs):
    maxnum = inputs[-1]
    # minnum = min(inputs[:-1])
    inputs.reverse()
    profs = []

    for i,n in enumerate(inputs[1:]):
        profs.append(maxnum - n)

        if n > maxnum and i != len(inputs) - 1:
            maxnum = n
            # print(maxnum)

        # if n >= maxnum and i != len(inputs) - 2:
        #     minnum = n
            # print("min changed at {} to {}".format(i, n))
            # maxnum = n
            # print(minnum)

    return max(profs)

if __name__ == "__main__":
    main()