#include <bits/stdc++.h>
using namespace std;

#define rep(i,n) for(long long i = 0; i < (long long)(n); i++)
#define pb push_back
#define all(x) (x).begin(), (x).end()
template<class T1, class T2> bool chmin(T1 &a, T2 b) { return b < a && (a = b, true); }
template<class T1, class T2> bool chmax(T1 &a, T2 b) { return a < b && (a = b, true); }
using ll = long long; using ld = long double; using vll = vector<ll>; using vld = vector<ld>;

static const long long INF = 1e18;

int main(void) {
    cin.tie(0); ios::sync_with_stdio(false);
    ll n, m; cin >> n >> m;
    vll a(m); rep(i, a.size()) cin >> a[i];
    sort(all(a));
    ll negnum = (ll)(upper_bound(all(a), 0) - a.begin());
    ll posnum = m - negnum;

    ll ret = INF;
    rep(j, n + 1) { // j個正のを取る
        if (j > posnum || n - j > negnum) continue;
        ll sp = 0; if (j != 0) sp = +a[negnum+j-1];
        ll sn = 0; if (j != n) sn = -a[negnum+j-n];
        chmin(ret, sp + sn * 2);
        chmin(ret, sn + sp * 2);
    }

    cout << ret << endl;
           
    return 0;
}