#include <algorithm>
#include <cstdio>
#include <cstdlib>
#include <cctype>
#include <cmath>
#include <iostream>
#include <queue>
#include <list>
#include <stack>
#include <map>
#include <numeric>
#include <set>
#include <sstream>
#include <string>
#include <vector>
using namespace std;
#define REP(i,a,n) for(int i=(a); i<(int)(n); i++)
#define rep(i,n) REP(i,0,n)
#define FOR(it,c) for(__typeof((c).begin()) it=(c).begin(); it!=(c).end(); ++it)
#define ALLOF(c) (c).begin(), (c).end()
typedef long long ll;

int main(){
  ios::sync_with_stdio(false);
  int N, M;
  cin >> N >> M;
  vector<int> vm, vp;
  bool zero = false;
  rep(i,M){
    int d;
    cin >> d;
    if(d > 0) vp.push_back(d);
    else if(d==0) zero = true;
    else vm.push_back(d);
  }
  if(vm.size()>0){
    sort(ALLOF(vm));
    reverse(ALLOF(vm));
  }
  if(zero) N--;
  if(vp.size()>0){
    sort(ALLOF(vp));
  }

  if(N==0){
    cout << 0 << endl;
    return 0;
  }

  int ret = 9999999;
  rep(i,min(N,(int)vp.size())+1){
    if(N-i>vm.size()) continue;
    int tmp_p = 0, tmp_m = 0;
    if(i>0) tmp_p = vp[i-1];
    if(N-i>0) tmp_m = -vm[N-i-1];
    ret = min(ret, tmp_p*2 + tmp_m);
  }
  rep(i,min(N,(int)vm.size())+1){
    if(N-i>vp.size()) continue;
    int tmp_p = 0, tmp_m = 0;
    if(i>0) tmp_m = -vm[i-1];
    if(N-i>0) tmp_p = vp[N-i-1];
    ret = min(ret, tmp_m*2 + tmp_p);
  }
  cout << ret << endl;
  
  return 0;
}