#include<iostream>
#include<algorithm>
using namespace std;

int main()
{
	int n, m, d[1001], i, j;

	cin >> n >> m;

	for (i = 1; i <= m; i++) cin >> d[i];

	sort(d + 1, d + m + 1);

	int ans = 10000;
	for (i = 1; i <= m - n + 1; i++)
	{
		if (d[i] < 0 && d[i + n - 1] <= 0) ans = min(ans, -d[i]);
		else if (d[i] < 0 && d[i + n - 1]>0) ans = min(ans, d[i + n - 1] - d[i] * 2);
		else ans = min(ans, d[i + n - 1]);
	}
	cout << ans << endl;
}