#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
#define rep(i, n) for(ll i = 0, i##_len = (n); i < i##_len; i++)
#define reps(i, s, n) for(ll i = (s), i##_len = (n); i < i##_len; i++)
#define rrep(i, n) for(ll i = (n) - 1; i >= 0; i--)
#define rreps(i, e, n) for(ll i = (n) - 1; i >= (e); i--)
#define all(x) (x).begin(), (x).end()
#define sz(x) ((ll)(x).size())
#define len(x) ((ll)(x).length())

int main() {
    cin.tie(0);
    ios::sync_with_stdio(false);
    // ifstream in("input.txt");
    // cin.rdbuf(in.rdbuf());
    ll n, m;
    cin >> n >> m;
    vector<ll> d(m);
    rep(i, m) cin >> d[i];
    sort(all(d));
    ll ans = LONG_LONG_MAX;
    rep(l, m) {
        reps(r, l, m) {
            ll dist = 0;
            if ((r - l + 1) < n) continue;
            if (((d[l] < 0) && (d[r] < 0)) || ((d[l] >= 0) && (d[r] >= 0))) {
                dist = max(abs(d[l]), abs(d[r]));
            }
            else {
                dist = min(abs(d[l]), abs(d[r])) + abs(d[l]) + abs(d[r]);
            }
            ans = min(ans, dist);
        }
    }
    cout << ans << endl;
    return 0;
}