Maximize Stock Profit

You are given a sequence of stock prices over consecutive days. Your task is to determine the maximum profit that can be made by performing a single buy and a single sell operation. In other words, you must choose two days i and j (with i < j) such that the difference between the price on day j and day i is maximized.

If no positive profit can be obtained, return 0.

You can mathematically represent the problem as finding

$$\max_{0\leq i<j<n}\{price[j]-price[i]\}$$

where price[k] represents the stock price on the kth day.

inputFormat

The input is read from stdin and consists of two lines:

• The first line contains a single integer N which represents the number of days (and hence the number of stock prices).
• The second line contains N space-separated integers, each representing the stock price on a day.

outputFormat

Output a single integer to stdout representing the maximum profit achievable from one transaction. If no profitable transaction is possible, output 0.

## sample

6
7 1 5 3 6 4

5

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