#include <bits/stdc++.h>

using namespace std;
#define FOR(i,n) for(int i = 0; i < (n); i++)
#define sz(c) ((int)c.size())
#define ten(n) ((int)1e##n)
using ll = long long;

int n, m;
int d[1000];

int main() {
	cin >> n >> m;
	FOR(i, m) cin >> d[i];
	sort(d, d + m);

	int ans = ten(8);
	FOR(l, m) {
		int r = l + n;
		if (r > m) break;
		r--;
		int t1 = abs(d[l]) + abs(d[l] - d[r]);
		int t2 = abs(d[r]) + abs(d[l] - d[r]);
		ans = min(ans, min(t1, t2));
	}
	cout << ans << endl;

	return 0;
}