#include <bits/stdc++.h>
#define rep(i, a, n) for(int i = a; i < n; i++)
#define repp(i, n) rep(i, 0, n)
#define repb(i, a, b) for(int i = a; i >= b; i--)
#define all(a) a.begin(), a.end()
#define int long long
using namespace std;
typedef pair<int, int> P;

signed main(){
    int n, m;
    cin >> n >> m;
    vector<int> d(m);
    rep(i, 0, m) cin >> d[i];
    sort(all(d));
    int ans = 10000000000;
    rep(i, 0, m - n + 1){
        int MIN, MAX, tmp = 0;
        MIN = d[i];
        MAX = d[i + n - 1];
        if(MIN * MAX < 0) tmp += 2 * min(abs(MIN), abs(MAX));
        tmp += max(abs(MIN), abs(MAX));
        // cout << tmp << endl;
        ans = min(ans, tmp);
    }
    cout << ans << endl;
}