Problem Statement

There are N cities on a number line. The i-th city is located at coordinate x_i.
Your objective is to visit all these cities at least once.
In order to do so, you will first set a positive integer D.
Then, you will depart from coordinate X and perform Move 1 and Move 2 below, as many times as you like:

• Move 1: travel from coordinate y to coordinate y + D.
• Move 2: travel from coordinate y to coordinate y - D.

Find the maximum value of D that enables you to visit all the cities.
Here, to visit a city is to travel to the coordinate where that city is located.

Input

Input is given from Standard Input in the following format:
N X
x_1 x_2 ... x_N

Output

Print the maximum value of D that enables you to visit all the cities.

Constraints

• All values in input are integers.
• $1 \leq N \leq 10^5$
• $1 \leq X \leq 10^9$
• $1 \leq x_i \leq 10^9$
• x_i are all different.
• $x_1, x_2, ..., x_N \neq X$

Sample Input 1

3 3
1 7 11

Sample Output 1

2

Setting D = 2 enables you to visit all the cities as follows, and this is the maximum value of such D.

• Perform Move 2 to travel to coordinate 1.
• Perform Move 1 to travel to coordinate 3.
• Perform Move 1 to travel to coordinate 5.
• Perform Move 1 to travel to coordinate 7.
• Perform Move 1 to travel to coordinate 9.
• Perform Move 1 to travel to coordinate 11.

Sample Input 2

3 81
33 105 57

Sample Output 2

24

Sample Input 3

1 1
1000000000

Sample Output 3

999999999

见题面 Input 部分

见题面 Output 部分