Author:  A. Klenin  Time limit:  3 sec  
Input file:  input.txt  Memory limit:  256 Mb  
Output file:  output.txt 
The main hall of the Nearsea Institute of Unspecified Underwater Studies has a shape of a long corridor. Along the corridor, there are N aquariums exhibiting various sea creatures. Aquariums are located at distances x_{1}, …, x_{N} from the hall entrance (x_{i} < x_{i + 1}).
The institute has recently got a new director, who decided that the aquarium maintenance is too costly, and issued an order to remove M (0 ≤ M ≤ N − 2) aquariums.
To minimize the disruption to the looks of the hall, it was decided that:
Your program must select aquariums for removal in such a way that the above conditions are satisfied.
Input file contains integers N M followed by N integers x_{i}.
Output file should contain a single integer — the smallest possible maximum distance.
No.  Input file (input.txt ) 
Output file (output.txt ) 

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