#include <bits/stdc++.h>
using namespace std;

#ifdef LOCAL
    #define eprintf(...) fprintf(stderr, __VA_ARGS__)
#else
        #define eprintf(...) 42
#endif

#define rep(i,n) for(int i=0;i<(int)(n);i++)
#define repi(i,a,b) for(int i=(int)(a);i<(int)(b);i++)
#define all(x) (x).begin(),(x).end()
#define foreach(u,v) for(auto (u) : (v))
#define pb push_back
#define mp make_pair
#define mt make_tuple

typedef long long ll;
typedef pair<int, int> pii;
typedef vector<int> vi;
typedef vector<vi> vvi;
typedef pair<ll, ll> pll;
typedef vector<ll> vl;

const int inf = 1e9;
const ll linf = 1LL<<60;
const ll mod = 1e9 + 7;
const double eps = 1e-9;

/*
*/

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

  vi d(m);
  rep(i, m){
    cin >> d[i]; 
  }

  sort(all(d));

  vi pos(1), neg;
  rep(i, m){
    if(d[i] > 0) pos.pb(d[i]);
    else if(d[i] == 0) n--;
    else neg.pb(d[i]);
  }

  if(n < 0){
    cout << 0 << endl;
    return 0;
  }
  
  neg.pb(0);
  reverse(all(neg));

  int ans = inf;
  if(n < pos.size()) ans = min(ans, pos[n]);
  if(n < neg.size()) ans = min(ans, -neg[n]);
  repi(i, 1, pos.size()){
    int j = n-i;
    if(j < 0 or j >= neg.size()) continue;
    ans = min(ans, 2*pos[i]-neg[j]);
    ans = min(ans, pos[i]-2*neg[j]);
  }

  cout << ans << endl;

  return 0;
}