#define _USE_MATH_DEFINES
#include <algorithm>
#include <cstdio>
#include <functional>
#include <iostream>
#include <cfloat>
#include <climits>
#include <cstdlib>
#include <cstring>
#include <cmath>
#include <map>
#include <queue>
#include <random>
#include <set>
#include <sstream>
#include <stack>
#include <string>
#include <time.h>
#include <vector>
using namespace std;

typedef long long ll;
typedef unsigned long long ull;
typedef pair<int, int> i_i;
typedef pair<ll, int> ll_i;
typedef pair<double, int> d_i;
typedef pair<ll, ll> ll_ll;
typedef pair<double, double> d_d;
typedef pair<int, ll> i_ll;
struct edge { int u, v; ll w; };

double INF = DBL_MAX / 10;
ll MOD = 1000000007;
ll _MOD = 1000000009;
double EPS = 1e-10;

int main() {
	int N, K; cin >> K >> N;
	vector<int> x(N);
	for (int i = 0; i < N; i++)
		cin >> x[i];
	sort(x.begin(), x.end());
	int mi = INT_MAX;
	for (int l = 0; l + K <= N; l++) {
		int r = l + K - 1;
		if (x[l] * x[r] < -1) mi = min(mi, abs(x[l]) + abs(x[r]) + min(abs(x[l]), abs(x[r])));
		else mi = min(mi, max(abs(x[l]), abs(x[r])));
	}
	cout << mi << endl;
}