#include "bits/stdc++.h"
#define _CRT_SECURE_NO_WARNINGS
#define rep(i,n) for(int i = 0;i < n;i++)
#define REP(i,n,k) for(int i = n;i < k;i++)
#define P(p) cout << (p) << endl;
#define sP(p) cout << setprecision(15) << fixed << p << endl;
#define Pi pair<int,int>
#define IINF 1e9
#define LINF 1e18
#define vi vector<int>
using namespace std;
typedef long long ll;
typedef unsigned long long ull;
int dx[] = { 1, 0,-1,0 };
int dy[] = { 0, 1,0,-1 };

void solve() {
	int n, m;
	cin >> n >> m;
	vi posn,posp;
	rep(i, m) {
		int a;
		cin >> a;
		if (a < 0) {
			posn.push_back(a);
		}
		else {
			posp.push_back(a);
		}
	}
	sort(posn.begin(), posn.end());
	reverse(posn.begin(), posn.end());
	sort(posp.begin(), posp.end());
	int dp[1010],l[1010],r[1010];
	rep(i, 1010) {
		l[i] = 1e9;
		r[i] = 1e9;
	}
	r[0] = 0;
	rep(i, posp.size()) {
		r[i + 1] = posp[i];
	}
	l[0] = 0;
	rep(i, posn.size()) {
		l[i + 1] = -posn[i];
	}
	rep(i, n+1) {
		dp[i] = min((l[i] * 2) + r[n - i], l[i] + (r[n - i] * 2));
	}
	int mini = 1e9;
	rep(i, n + 1) {
		mini = min(mini, dp[i]);
	}
	P(mini);
}

int main() {
	solve();
	return 0;
}