#include <bits/stdc++.h>
using namespace std;

// 基本テンプレート
struct cww{cww(){ios::sync_with_stdio(false);cin.tie(0);}}star;
#define P(x) cout << (x) << endl
#define p(x) cout << (x)
#define all(c) (c).begin(), (c).end()
#define rall(c) (c).rbegin(), (c).rend()
#define mat(type, c, m, n) vector<vector<type>> c(m, vector<type>(n));for(auto& r:c)for(auto& i:r)cin>>i;
#define rep(i,a,n) for(int i=(a), i##_len=(n); i<i##_len; ++i)
#define rrep(i,a,n) for(int i=(a); i>n; --i)
#define each(x,y) for(auto &(x):(y))
#define perm(c) sort(all(c));for(bool c##p=1;c##p;c##p=next_permutation(all(c)))
#define cauto const auto&
#define UNIQUE(v) v.erase( unique(all(v)), v.end() );
#define len(x) ((int)(x).size())
#define length(a)   (sizeof(a)/sizeof(a[0]))
template<typename T> inline bool inside(T y, T x, T h, T w) { return 0 <= y && y < h && 0 <= x && x < w; };

// デバッグ用
inline void print() {cout << endl;}
template <class H, class... T> inline void print(H h, T... t){cout << h << " ";print(t...);}
#define dbg(v) for(auto i : v) cout << i << " "; cout << endl;

// 型
typedef long long ll;
typedef vector<int> vi;
typedef vector<double> vd;
typedef vector<long long> vll;
typedef vector<string> vs;
typedef vector<bool> vb;

ll mod = (int)1e9 + 7;

// 定数
#define PI acos(-1.0)
//constexpr int EPS = (1e-9);
//constexpr int INF = 100000000;

// 4近傍
constexpr int dx[] = {1, 0, -1, 0};
constexpr int dy[] = {0, 1, 0, -1};


// 8近傍
//constexpr int dy[]={0,0,1,-1,1,1,-1,-1};
//constexpr int dx[]={1,-1,0,0,1,-1,1,-1};

//constexpr int MAX = 1005;

//int g0 = 0;
//vi fv, pv;


int f() {
	int n, m; cin >> n >> m;

	vi v(m); rep(i, 0, m) cin >> v[i];
	sort(all(v));

	int h, k = 0, ans = 1e9;
	rep(i, 0, m - n + 1) {
		h = v[i + n - 1];
		if (0 <= v[i]) k = h;
		else if (h < 0) k = abs(v[i]);
		else k = min(abs(v[i]) * 2 + h, abs(v[i]) + h * 2);
		ans = min(ans, k);
	}
	return ans;
}

int main() {
//	cout << setprecision(12) << fixed;

	P(f());

	return 0;
}