In math, derivative is the change between states. In image processing, when calculating the derivative of a series of numbers previous number is subtracted from this number. And the result is written into this position.

Question: Write a program that reads an array, and then calculates the the biggest change in the new array.

Input specification
In the first line, you will be given one integer: array length (n). Then, in the following n lines you will be given n integers where each number is between -2e4 and 2e4 and 0 ≤ n ≤ 30,000.

Output specification:
Show one integer: the biggest change in the derivative of the array.
Note: Assume that you have zero (0) before the first number.

Explanation: The difference array contains (difference between a_i and a_i-1) : 15, 37, 23, 41, 6.
So, the biggest change is 41.