#include<iostream>
#include<string>
#include<algorithm>
#include<cctype>
#include<set>
#include<bitset>
#include<math.h>
#include<map>
#include<queue>
#include<iomanip>
using namespace std;
using ll = long long;

int main()
{
    int n, m, min1 = 100000;
    cin >> n >> m;
    vector<int> v(m);
    for (int i = 0; i < m; i++) cin >> v[i];
    sort(v.begin(), v.end());

    for (int i = 0; i < m-n+1; i++){
        int temp = 0;
        if ((v[i] >= 0) || v[i+n-1] <= 0) temp = max(abs(v[i+n-1]), abs(v[i]));
        else if ((v[i+n-1] > 0 && v[i] < 0)) temp = max(abs(v[i+n-1]), abs(v[i])) + min(abs(v[i+n-1]), abs(v[i]))*2;
        min1 = min(min1, temp);
    }
    cout << min1 << endl;
}