#include<cstdio>
#include<iostream>
#include<algorithm>
#include<string>
#include<queue>
#include<vector>
#include<functional>
#include<cmath>
#include<map>
#include<stack>
#include<set>
#include<numeric>

using namespace std;
typedef long long ll;
typedef pair<int, int> pi;
typedef pair<ll, ll> pl;

int main()
{
	int N, M;
	cin >> N >> M;
	
	int d[1010] = {0};
	int ds[1010] = {0};
	bool zeroflag = 0;

	for (int i = 0; i < M; i++) {
		cin >> d[i];
		if (d[i] == 0)zeroflag = 1;
	}

	if (zeroflag)N--;
	sort(d, d + M);
	
	ds[0] = 0;
	for (int i = 1; i < M; i++) 
		ds[i] += ds[i-1] + d[i] - d[i-1];

	int mi = 1000000;

	if (N == 1) {
		for (int i = 0; i < M; i++) {
			if (d[i] == 0) {
				mi = min(d[i] - d[i - 1], d[i + 1] - d[i]);
			}
		}
	}
	else {
		for (int i = 1; i <= M - N; i++) {
			if (mi > ds[i + (N - 1)] - ds[i] + abs(d[i - 1])) {
				mi = ds[i + (N - 1)] - ds[i] + abs(d[i - 1]);
			}
		}
	}
	cout << mi << endl;
	
	return 0;
}