#include <stdio.h>
int N_site[ 50001 ] ;

void swap( int *a , int *b ){
	int tmp = *a ;
	*a = *b ;
	*b = tmp ;
}
void sot ( int N )
{
	for ( int i = 0 ; i < N ; i ++ )
		for ( int j = i ; j >= 0 ; j-- )
			if ( N_site[ j ] < N_site[ j - 1 ] )
				swap ( &N_site[ j ] , &N_site[ j - 1 ] ) ;
}
int try_1 ( int R , int N , int K )
{
	int num = 0 ;
	int site ;
	
	for ( int i = 0 ; i < N ; ){
		site = N_site[ i ] + R ;
		num += 1 ;
		if ( num > K )
			return 0 ;
		if ( N_site[ N - 1 ] <= site )
			return 1 ;
		while( N_site[ i ] <= site )
			i++ ;
	}
}
int main()
{
	int R , N , K ;
	while( scanf( "%d %d" , &N , &K ) != EOF ){
		for ( int i = 0 ; i < N ; i++ )
			scanf( "%d" , &N_site[ i ] ) ;
		sot( N ) ;
		
		R = N_site[ N - 1 ] - N_site[ 0 ] ;
		while ( try_1( R - 1 , N , K ) )
			R-- ;
		printf ( "%d\n" , R ) ;
	}
	return 0 ;
}

#include 
int N_site[ 50001 ] ;

void swap( int *a , int *b ){
	int tmp = *a ;
	*a = *b ;
	*b = tmp ;
}
void sot ( int N )
{
	for ( int i = 0 ; i < N ; i ++ )
		for ( int j = i ; j >= 0 ; j-- )
			if ( N_site[ j ] < N_site[ j - 1 ] )
				swap ( &N_site[ j ] , &N_site[ j - 1 ] ) ;
}
int try_1 ( int R , int N , int K )
{
	int num = 0 ;
	int site ;
	
	for ( int i = 0 ; i < N ; ){
		site = N_site[ i ] + R ;
		num += 1 ;
		if ( num > K )
			return 0 ;
		if ( N_site[ N - 1 ] <= site )
			return 1 ;
		while( N_site[ i ] <= site )
			i++ ;
	}
}
int main()
{
	int R , N , K ;
	while( scanf( "%d %d" , &N , &K ) != EOF ){
		for ( int i = 0 ; i < N ; i++ )
			scanf( "%d" , &N_site[ i ] ) ;
		sot( N ) ;
		
		R = N_site[ N - 1 ] - N_site[ 0 ] ;
		while ( try_1( R - 1 , N , K ) )
			R-- ;
		printf ( "%d\n" , R ) ;
	}
	return 0 ;
}

排序建議不要用bubble_sort，效率太差，要改用如merge_sort會內建等複雜度O(nlogn)的演算法