#include <iostream>
#include <vector>
#include <algorithm>
using namespace std;

#define RREP(i,s,e) for (i = s; i >= e; i--)
#define rrep(i,n) RREP(i,(int)(n)-1,0)
#define REP(i,s,e) for (i = s; i <= e; i++)
#define rep(i,n) REP(i,0,(int)(n)-1)
#define INF 100000000

typedef long long ll;

int main() {
    int i, n, m, ans;
    int d[10000];
    cin >> n >> m;
    rep (i,m) cin >> d[i];
    sort(d,d+m);
    ans = INF;
    rep (i,m) {
        if (d[i] < 0 && i+n-1 < m) {
            if (d[i+n-1] < 0)
                ans = min(ans,-d[i]);
            else
                ans = min({ans,-d[i]*2+d[i+n-1],-d[i]+d[i+n-1]*2});
        }
        else if (d[i] >= 0 && i+n-1 < m)
            ans = min(ans,d[i+n-1]);
    }
    cout << ans << endl;
    return 0;
}