//http://yukicoder.me/problems/780
#include <cmath>
#include <cstdio>
#include <vector>
#include <iostream>
#include <algorithm>
#include <functional>
#include <map>
#include <set>
#include <deque>
#include <queue>
#include <limits>
#include <sstream>
#include <typeinfo>

using namespace std;

int main() {
	int N, M;
	cin >> N >> M;
	vector<long long> D(M);
	for (int i = 0; i < M; i++) {
		cin >> D[i];
	}
	sort(D.begin(), D.end());

	long long ans = 1000000000;
	for (int i = 0; i < M - N; i++) {
		int j = i + N - 1;
		long long t = 0;
		if (D[i] <= 0 && 0 <= D[j]) {
			if (abs(D[i]) < abs(D[j]))
				t = abs(D[i]) * 2 + abs(D[j]);
			else
				t = abs(D[i]) + abs(D[j]) * 2;
		} else {
			if (abs(D[i]) < abs(D[j]))
				t = abs(D[j]);
			else
				t = abs(D[i]);
		}
		ans = min(ans, t);
	}

	cout << ans << endl;
	return 0;
}