#include<iostream>
#include<cstdio>
#include<cstring>
#include <cstdlib>  
#include <cmath>   
#include<cctype>
#include<string>
#include<set>
#include<iomanip>
#include <map>
#include<algorithm>
#include <functional>
#include<vector>
#include<climits>
#include<stack>
#include<queue>
#include <deque>
#include <climits>
#include <typeinfo>
#include <utility> 
#define all(x) (x).begin(),(x).end()
#define rep(i,m,n) for(int i = m;i < n;++i)
#define pb push_back
#define fore(i,a) for(auto &i:a)
#define rrep(i,m,n) for(int i = m;i >= n;--i)
#define INF INT_MAX/2
using namespace std;
using ll = long long;
using R = double;
using Data = pair<ll, vector<int>>;
const ll MOD = 1e9 + 7;
const ll inf = 1LL << 50;
struct edge { ll from; ll to; ll cost; };


int main() {
	int n, m;
	cin >> n >> m;
	vector<int>D(m);
	rep(i, 0, m)cin >> D[i];

	sort(all(D));

	if (D[0] >= 0) {
		cout << D[n - 1] << endl;
	}
	else if(D[m-1] <= 0){
		cout << -D[m - n] << endl;
	}
	else {
		int ans = 1000000010;
		vector<int>Dpl;
		vector<int>Dmi;
		rep(i, 0, m) {
			if (D[i] >= 0)Dpl.pb(D[i]);
			else Dmi.pb(D[i]);
		}
		reverse(all(Dmi));


		rep(i, 0, Dpl.size()) {
			if (n-i-2 >= 0 && n-i-2 <= Dmi.size()-1) {
				ans = min(ans, 2 * Dpl[i] - Dmi[n-i-2]);
			}
		}
		rep(i, 0, Dmi.size()) {
			if (n - i - 2 >= 0 && n-i-2 <= Dpl.size()-1) {
				ans = min(ans, (-2) * Dmi[i] + Dpl[n-i-2]);
			}
		}

		if (Dpl.size() >= n) {
			ans = min(ans,Dpl[n-1]);
		}
		if (Dmi.size() >= n) {
			ans = min(ans,-Dmi[n - 1]);
		}
		cout << ans << endl;
	}


	return 0;
}