Minimum Modular
Description
You have been given n distinct integers a1, a2, ..., an. You can remove at most k of them. Find the minimum modular m (m > 0), so that for every pair of the remaining integers (ai, aj), the following unequality holds: 
.
The first line contains two integers n and k (1 ≤ n ≤ 5000, 0 ≤ k ≤ 4), which we have mentioned above.
The second line contains n distinct integers a1, a2, ..., an (0 ≤ ai ≤ 106).
Print a single positive integer — the minimum m.
Input
The first line contains two integers n and k (1 ≤ n ≤ 5000, 0 ≤ k ≤ 4), which we have mentioned above.
The second line contains n distinct integers a1, a2, ..., an (0 ≤ ai ≤ 106).
Output
Print a single positive integer — the minimum m.
Samples
7 0
0 2 3 6 7 12 18
13
7 1
0 2 3 6 7 12 18
7