#include <bits/stdc++.h>

using namespace std;

typedef long long ll;
typedef vector<int> vi;
typedef vector<ll> vl;
typedef complex<double> P;
typedef pair<int,int> pii;
#define REP(i,n) for(ll i=0;i<n;++i)
#define REPR(i,n) for(ll i=1;i<n;++i)
#define FOR(i,a,b) for(ll i=a;i<b;++i)

#define DEBUG(x) cout<<#x<<": "<<x<<endl
#define DEBUG_VEC(v) cout<<#v<<":";REP(i,v.size())cout<<" "<<v[i];cout<<endl
#define ALL(a) (a).begin(),(a).end()

#define MOD (ll)(1e9+7)
#define ADD(a,b) a=((a)+(b))%MOD
#define FIX(a) ((a)%MOD+MOD)%MOD

int n,m;
int d[1001];

int main(){
  scanf("%d%d",&n,&m);
  REP(i,m)scanf("%d",d+i);
  sort(d,d+m);
  int mn = 830252521;
  REP(i,m-n+1){
    int lmost = d[i];
    int rmost = d[i+n-1];
    if(rmost<=0||0<=lmost){
      mn=min(mn,max(abs(rmost),abs(lmost)));
    }else{
      int x = abs(lmost);
      int y = abs(rmost);
      if(x>y)swap(x,y);
      mn=min(mn,2*x+y);
    }
  }
  printf("%d\n",mn);
  return 0;
}