#include <bits/stdc++.h>

using namespace std;
using ll = long long;
using PII = std::pair<int, int>;
using PLL = std::pair<ll, ll>;

#define rep(i, n) for (int i = 0; i < (int)(n); i++)
// #define rep2(i, s, n) for (int i = (s); i < (int)(n); i++)
// #define DEBUG



int main()
{

#ifdef DEBUG
    cout << "DEBUG MODE" << endl;
    ifstream in("input.txt"); //for debug
    cin.rdbuf(in.rdbuf());    //for debug
#endif

    int n, m, d, l, r, ans;
    cin >> n >> m;

    vector<int> gabage;
    rep(i, m)
    {
        cin >> d;
        gabage.push_back(d);
    }
    sort(gabage.begin(), gabage.end());

    ans = 1e9+7;
    rep(i, n)
    {
        l = gabage[i];
        r = gabage[i + n - 1];

        if (l * r < 0)
            ans = min(ans, abs(l) + abs(r) + min(abs(l), abs(r)));
        else
            ans = min(ans, max(abs(l), abs(r)));
    }
    cout << ans << endl;
    
    return 0;
}