#define _CRT_SECURE_NO_WARNINGS
#include <iostream>
#include <climits>
#include <cmath>
#include <string>
#include <vector>
#include <algorithm>
#include <queue>
#include <map>
#include <functional>
#include <set>
#include <numeric>
#include <stack>
#include <utility>
#include <time.h>
#include <iterator>
//#include "util.h"

using namespace std;
typedef unsigned uint;
typedef long long ll;
typedef unsigned long long ull;



//呪文
template <typename _KTy, typename _Ty> ostream& operator << (ostream& ostr, const pair<_KTy, _Ty>& m) { cout << "{" << m.first << ", " << m.second << "}"; return ostr; }
template <typename _KTy, typename _Ty> ostream& operator << (ostream& ostr, const map<_KTy, _Ty>& m) { if (m.empty()) { cout << "{ }"; return ostr;	} cout << "{" << *m.begin(); for (auto itr = ++m.begin(); itr != m.end(); itr++) { cout << ", " << *itr; } cout << "}"; return ostr; }
template <typename _Ty> ostream& operator << (ostream& ostr, const vector<_Ty>& v) { if (v.empty()) { cout << "{ }"; return ostr; }	cout << "{" << v.front(); for (auto itr = ++v.begin(); itr != v.end(); itr++) { cout << ", " << *itr; }	cout << "}"; return ostr; }
template <typename _Ty> ostream& operator << (ostream& ostr, const set<_Ty>& s) { if (s.empty()) { cout << "{ }"; return ostr; } cout << "{" << *(s.begin()); for (auto itr = ++s.begin(); itr != s.end(); itr++) { cout << ", " << *itr; }	cout << "}"; return ostr; }
template <typename T> void print(T* v, int N) { if (N == 0) cout << "{ }"; cout << "{" << v[0]; for (int i = 1; i < N; i++) cout << ", " << v[i]; cout << "}"; }
#define PI 3.14159265358979323846
#define EPS 1e-8
#define MIN(a,b) ((a)<(b)?(a):(b))
#define MAX(a,b) ((a)>(b)?(a):(b))
#define all(x) (x).begin(), (x).end()



#define INF 99999

int yuki0370()
{
	int N, M;
	cin >> N >> M;

	bool zero = false;
	vector<int> right, left; // 左右に落ちている i 個目のゴミの位置
	right.push_back(0); left.push_back(0);

	int D;
	for (int i = 0; i < M; i++) {
		cin >> D;
		if (D < 0) 
			left.push_back(-D);
		else if (D > 0)
			right.push_back(D);
		else
			zero = true;
	}
	sort(all(right));
	sort(all(left));

	int ans = INF;
	// ゴミが 0 に落ちている
	if (zero) N--;
	// 右のゴミを r 個拾うとき
	for (int r = 0; r <= min(N, (int)(right.size() - 1)); r++) {

		// 左のゴミは N - r 個拾う
		int l = N - r;
		// 拾えない
		if (l >= left.size()) continue;

		int dist;

		// 右のみ拾う
		if (l == 0)
			dist = right[r];
		// 左のみ拾う
		else if (r == 0)
			dist = left[l];
		// 右から拾う場合と左から拾う場合
		else
			dist = min(2 * right[r] + left[l], 2 * left[l] + right[r]);

		// 最短距離更新
		if (ans > dist) ans = dist;
	}

	cout << ans << endl;

	return 0;
}

int main()
{
	//clock_t start, end;
	//start = clock();

	yuki0370();
	
	//end = clock();
	//printf("%d msec.\n", end - start);

	return 0;
}