#include<iostream>
#include<algorithm>
using namespace std;
#define REP(i, a, n) for(int i=a; i<n; i++)
#define RREP(i, a, n) for(int i=n-1; i>=a; i--)
#define INF 1000000000
#define ll long long

int main()
{
	int N, M;
	int D[1001];
	cin >> N >> M;
	REP(i, 0, M) cin >> D[i];

	sort(D, D + M);

	int ans = INF;
	REP(i, 0, M - N + 1) {
		int dist = D[i + N - 1] - D[i];
		ans = min(ans, dist + min(abs(D[i + N - 1]), abs(D[i])));
	}

	cout << ans << endl;
	return 0;
}