#include <bits/stdc++.h>
using namespace std;

int main() {
	int n, m;
	cin >> n >> m;

	vector<int> a, b;
	for (int i = 0; i < m; i++) {
		int d;
		cin >> d;
		if (d == 0) n--;
		else if (d > 0) a.push_back(d);
		else b.push_back(d);
	}
	sort(a.begin(), a.end());
	sort(b.rbegin(), b.rend());

	int ans = 1e9;
	for (int i = 0; i <= n; i++) {
		int j = n - i;
		int cand = 0;
		int x = 0;
		int num = 0;
		for (int k = 0; k < min<int>(i, a.size()); k++) {
			num++;
			cand += abs(a[k] - x);
			x = a[k];
		}
		for (int k = 0; k < min<int>(j, b.size()); k++) {
			num++;
			cand += abs(b[k] - x);
			x = b[k];
		}
		if (num == n)
			ans = min(ans, cand);
	}
	for (int i = 0; i <= n; i++) {
		int j = n - i;
		int cand = 0;
		int x = 0;
		int num = 0;
		for (int k = 0; k < min<int>(j, b.size()); k++) {
			num++;
			cand += abs(b[k] - x);
			x = b[k];
		}
		for (int k = 0; k < min<int>(i, a.size()); k++) {
			num++;
			cand += abs(a[k] - x);
			x = a[k];
		}
		if (num == n)
			ans = min(ans, cand);
	}
	cout << ans << endl;
}