#define _USE_MATH_DEFINES
#include <cstdio>
#include <iostream>
#include <sstream>
#include <fstream>
#include <iomanip>
#include <algorithm>
#include <cmath>
#include <complex>
#include <string>
#include <vector>
#include <list>
#include <queue>
#include <stack>
#include <set>
#include <map>
#include <bitset>
#include <numeric>
#include <limits>
#include <climits>
#include <cfloat>
#include <functional>
using namespace std;

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

    int ans = INT_MAX;
    for(int i=0; i<=m-n; ++i){
        int a = d[i];
        int b = d[i+n-1];

        int dist;
        if(b < 0)
            dist = -a;
        else if(0 < a)
            dist = b;
        else
            dist = b - a + min(-a, b);
        ans = min(ans, dist);
    }
    cout << ans << endl;

    return 0;
}