#include <iostream>
#include <fstream>
#include <vector>
#include <cstring>
#include <string>
#include <algorithm>
#include <iomanip>
using namespace std;

int main() {
	cin.tie(0);
	ios::sync_with_stdio(false);

	int N, M;
	cin >> N >> M;

	vector<int> left, right;
	for(int i = 0; i < M; i++) {
		int D;
		cin >> D;
		if(D < 0) left.push_back(-D);
		else if(D > 0) right.push_back(D);
		else N--;
	}
	sort(left.begin(), left.end());
	sort(right.begin(), right.end());

	int ans = 1 << 25;
	for(int i = 0; i < left.size() + 1; i++) {
		int rem = N - i, leftLen = 0, rightLen = 0;
		if(rem > right.size()) continue;
		if(i > 0) {
			leftLen = left[i - 1];
		}
		if(rem > 0) {
			rightLen = right[rem - 1];
		}
		ans = min(ans, min(2 * leftLen + rightLen, 2 * rightLen + leftLen));
	}

	cout << ans << endl;
}