#include <algorithm>
#include <cmath>
#include <iostream>

using namespace std;

int main(int argc, const char* argv[])
{
	int N, M;
	cin >> N >> M;
	int D[M];
	for (auto&& d : D) cin >> d;
	sort(D, &D[M]);
	int minval = 10000 * 3;
	for (int i = 0; i <= M - N; i++) {
		int lv = abs(min(D[i], 0));
		int rv = abs(max(D[i + N - 1], 0));
		minval = min(minval, min(lv * 2 + rv, lv + rv * 2));
	}
	cout << minval << endl;
	return 0;
}