#include <iostream>
#include <cstdio>
#include <vector>
#include <algorithm>
#include <utility>
#include <string>

using namespace std;

const int INF = 1e8;

int main() {
	int n, m, d;

	cin >> n >> m;
	vector<int> d_plus, d_minus;
	for (int i = 0; i < m; i++) {
		cin >> d;
		if (d >= 0) {
			d_plus.emplace_back(d);
		} else {
			d_minus.emplace_back(abs(d));
		}
	}
	sort(d_plus.begin(), d_plus.end());
	sort(d_minus.begin(), d_minus.end());

	while (d_plus.size() < n) {
		d_plus.emplace_back(INF);
	}
	while (d_minus.size() < n) {
		d_minus.emplace_back(INF);
	}

	int min_len = min(d_plus[n - 1], d_minus[n - 1]);
	for (int i = 0; i < n - 1; i++) {
		min_len = min({min_len, 2 * d_plus[i] + d_minus[n - 2 - i], d_plus[i] + 2 * d_minus[n - 2 - i]});
	}

	cout << min_len << endl;
	return 0;
}