#include <bits/stdc++.h>
#define int long long
//#define USE_FREOPEN
//#define MUL_TEST
#define FILENAME "clean"
using namespace std;
int a[1005];

void solve() {
	int n,m;
	cin >> n >> m;
	for (int i = 1; i <= m; i++) {
		cin >> a[i];
	}
	sort(a + 1,a + m + 1);
	
	int minn = 9e18;
	for (int i = 1; i <= m - n + 1; i++) {
		if (a[i] >= 0) {
			minn = min(minn,a[i + n - 1]);
		} else if (a[i + n - 1] <= 0) {
			minn = min(minn,-a[i]);
		} else {
			minn = min(minn,2 * min(-a[i],a[i + n - 1]) + max(-a[i],a[i + n - 1]));
		}
	}
	cout << minn << '\n';
}

signed main() {
	ios::sync_with_stdio(false);
	cin.tie(nullptr); cout.tie(nullptr);

	#ifdef USE_FREOPEN
		freopen(FILENAME ".in","r",stdin);
		freopen(FILENAME ".out","w",stdout);
	#endif
	int _ = 1;
	#ifdef MUL_TEST
		cin >> _;
	#endif
	while (_--)
		solve();
	_^=_;
	return 0^_^0;
}