#ifdef LOCAL111
#else
	#define NDEBUG
#endif
#include <bits/stdc++.h>
const int INF = 1e8;
using namespace std;

#define endl '\n'
#define ALL(a)  (a).begin(),(a).end()
#define SZ(a) int((a).size())
#define FOR(i,a,b) for(int i=(a);i<(b);++i)
#define RFOR(i,a,b) for (int i=(b)-1;i>=(a);i--)
#define REP(i,n)  FOR(i,0,n)
#define RREP(i,n) for (int i=(n)-1;i>=0;i--)
#define RBP(i,a) for(auto& i : a)
#ifdef LOCAL111
	#define DEBUG(x) cout<<#x<<": "<<(x)<<endl
#else
	#define DEBUG(x) true
#endif
#define F first
#define S second
#define SNP string::npos
#define WRC(hoge) cout << "Case #" << (hoge)+1 << ": "
#define rangej(a,b,c) ((a) <= (c) and (c) < (b))
#define rrangej(b,c) rangej(0,b,c)
template<typename T> void pite(T a, T b){ for(T ite = a; ite != b; ite++) cout << (ite == a ? "" : " ") << *ite; cout << endl;}
template<typename T> bool chmax(T& a, T b){if(a < b){a = b; return true;} return false;}
template<typename T> bool chmin(T& a, T b){if(a > b){a = b; return true;} return false;}

typedef pair<int,int> P;
typedef long long int LL;
typedef unsigned long long ULL;
typedef pair<LL,LL> LP;

void ios_init(){
	//cout.setf(ios::fixed);
	//cout.precision(12);
#ifdef LOCAL111
	return;
#endif
	ios::sync_with_stdio(false); cin.tie(0);	
}

int main()
{
	ios_init();
	int n,m;
	cin >> m >> n;
	vector<int> d(n);
	REP(i,n) cin >> d[i];	
	sort(ALL(d));
	int p = lower_bound(ALL(d),0)-d.begin();
	int ans = INF;
	REP(i,n){
		DEBUG(i);
		int cp = p;
		int cnt = 0;
		int dist = 0;
		if(d[i] < 0) cp--;
		int dir = (d[i] < 0 ? -1 : 1);
		DEBUG(dir);
		cnt = 1;
		dist += abs(d[cp]);
		int pre = d[cp];
		int sp = cp;
		while(cnt < m){
			DEBUG(cp);
			if(cp == i){
				pre = d[sp];
				dist = dist*2-d[sp];
				cp = sp;
				dir *= -1;
			}
			cp += dir;
			if(!(0 <= cp and cp < n)){
				DEBUG(1);
				break;
			}
			cnt++;
			dist += abs(pre-d[cp]);
			pre = d[cp];
		}
		if(cnt == m) ans = min(ans,dist);
		DEBUG(ans);
	}
	cout << ans << endl;
	return 0;
}