/* -*- coding: utf-8 -*-
 *
 * 370.cc: No.370 道路の掃除 - yukicoder
 */

#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<cmath>
#include<iostream>
#include<string>
#include<vector>
#include<map>
#include<set>
#include<stack>
#include<list>
#include<queue>
#include<deque>
#include<algorithm>
#include<numeric>
#include<utility>
#include<complex>
#include<functional>
 
using namespace std;

/* constant */

const int MAX_M = 1000;
const int INF = 1 << 30;

/* typedef */

/* global variables */

int ps[MAX_M + 1], ms[MAX_M + 1];
bool zero = false;

/* subroutines */

/* main */

int main() {
  int n, m;
  cin >> n >> m;

  int pn = 0, mn = 0;
  for (int i = 0; i < m; i++) {
    int di;
    cin >> di;
    if (di > 0) ps[++pn] = di;
    else if (di < 0) ms[++mn] = -di;
    else zero = true;
  }
  //printf("pn=%d,mn=%d\n", pn, mn);

  if (zero) n--;
  sort(ps, ps + pn + 1);
  sort(ms, ms + mn + 1);

  int mind = INF, maxi = min(n, mn);
  for (int i = 0, j = n; i <= maxi; i++, j--)
    if (j <= pn) {
      int d0 = ms[i] * 2 + ps[j];
      int d1 = ms[i] + ps[j] * 2;
      //printf("ms[%d]=%d,ps[%d]=%d:%d,%d\n", i, ms[i], j, ps[j], d0, d1);
      if (mind > d0) mind = d0;
      if (mind > d1) mind = d1;
    }

  printf("%d\n", mind);
  return 0;
}