#include <bits/stdc++.h>

#define mp       make_pair
#define mt	 make_tuple
#define pb       push_back
#define rep(i,n) for(int i=0;i<(n);i++)

using namespace std;

typedef    long long          ll;
typedef    unsigned long long ull;
typedef    pair<int,int>      pii;
typedef    pair<long,long>    pll;

const int INF=1<<29;
const double EPS=1e-9;
const int MOD = 100000007;

const int dx[]={1,0,-1,0},dy[]={0,-1,0,1};
int N,M;
vector<int> D;
int main(){
  cin >> N >> M;
  D.resize(M);
  for(auto &val : D){
    cin >> val;
  }

  sort(D.begin(), D.end());
  int result = INF;
  for (int i = 0; i < D.size(); i++){
    for (int j = i; j < D.size(); j++){
      int a = D[i];
      int b = D[j];
      int res = abs(i - j) + 1;
      if (res < N)continue;
      if (a < 0 and b < 0){
	result = min(result, abs(a));

      }
      if (a < 0 and b >= 0){
	result = min(result, abs(a) + abs(a) + b);
	result = min(result, b + b + abs(a));
      }
      if (a >= 0 and b >= 0){
	result = min(result, abs(b));
      }
    }
  }
  cout << result << endl;
}