#include <iostream>
#include <vector>
#include <algorithm>
#include <cstdlib>
using namespace std;

int main()
{
	int n,m;
	vector<int>gomi;
	int first,sum,min,d,z;

	cin >> n >> m;
	gomi.resize(m);

	cin >>gomi[0];
	first = abs(gomi[0]);
	for(int i=1;i<m;i++){
		cin>>gomi[i];
		z = abs(gomi[i]);
		if(first > z){
			first = z;
		}
	}
	
	sort(gomi.begin(),gomi.end());

	d = gomi[n-1] - gomi[0];
	for(int j=1;j<m-n+1;j++){
		min = gomi[j+n-1] - gomi[j];
		if(d>min){
			d=min;
		}
	}

	sum = first + d;

	cout << sum << endl;

	return 0;
}