#define _USE_MATH_DEFINES
#include<stdio.h>
#include<string>
#include<iostream>
#include<cctype>
#include<cstdio>
#include<vector>
#include<stack>
#include<queue>
#include <algorithm>
#include<math.h>
#include<set>
#include<map>
#include<iomanip>

//#include<bits/stdc++.h>



using namespace std;


int main() {

	int n, m;
	cin >> n >> m;
	int s = 0;
	vector<int>a, b;
	for (int i = 0; i < m; i++) {
		int x;
		cin >> x;
		a.push_back(x);
		if (!x)s++;
	}
	if (s == n) {
		cout << 0 << endl; return 0;
	}
	sort(a.begin(), a.end());
	
	int t = 99999999;
	for (int i = 0; i < a.size() - n+1; i++) {
		int r;
		if (a[i] < 0) {
		
			if (a[i +n - 1] <= 0)r = abs(a[i]);
			else r = abs(a[i]) * 2 + a[i+n-1];
		}
		else r = a[i + n - 1];
		t = min(t, r);
		//cout << i << "#" ;
	}

	for (int i = a.size()-1; i >= n-1; i--) {
		int r;
		if (a[i] > 0) {

			if (a[i - n+ 1] >= 0)r = abs(a[i]);
			else r = abs(a[i]) * 2 + abs(a[i - n + 1]);
		}
		else break;
		t = min(t, r);
	//	cout << i;
	}

	cout << t << endl;

	return 0;


}