#include <bits/stdc++.h>
using namespace std;
#define rep(i,a,b) for(int i=a;i<b;i++)
typedef long long ll;

int solve(int N, int M)
{
	vector<int> plus, minus;

	rep(i, 0, M)
	{
		int d; cin >> d;
		if (d == 0)
			N--;
		else if (d < 0)
			minus.push_back(-d);
		else
			plus.push_back(d);
	}

	if (N <= 0) return 0;

	minus.push_back(0);
	plus.push_back(0);
	sort(minus.begin(), minus.end());
	sort(plus.begin(), plus.end());

	int ans = INT_MAX;
	rep(i, 0, N + 1)
	{
		if (plus.size() <= i) continue;
		if (minus.size() <= N - i) continue;

		int c = plus[i] + minus[N - i] + min(plus[i], minus[N - i]);
		ans = min(ans, c);
	}

	return ans;
}

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

	int N, M;
	while (cin >> N >> M)
	{
		cout << solve(N, M) << endl;
	}
}