#include <algorithm>
#include <cstdio>
#include <iostream>
#include <map>
#include <cmath>
#include <queue>
#include <set>
#include <sstream>
#include <stack>
#include <string>
#include <vector>
#include <stdlib.h>
#include <stdio.h>
#include <bitset>
using namespace std;
#define FOR(I,A,B) for(int I = (A); I < (B); ++I)
typedef long long ll;

int main(){
  int N, M;
  cin >> N >> M;
  vector<int> D;
  int r = 0, l = 0;
  FOR (i,0,M) {
    int d;
    cin >> d;
    if (d < 0) {
      l++;
      D.push_back(d);
    }
    else if (d > 0) {
      r++;
      D.push_back(d);
    }
    else N--;
  }
  sort(D.begin(), D.end());
  int ans = 10000000;
  for (int i = 0; i + N - 1 < D.size(); i++) {
    if(D[i] > 0) {
      ans = min(ans, D[i+N-1]);
    }
    else if(D[i+N-1] < 0) {
      ans = min(ans, -D[i]);
    }
    else {
      ans = min(ans, 2 * D[i+N-1] + abs(D[i]));
      ans = min(ans, 2 * abs(D[i]) + D[i+N-1]);
    }
  }
  cout << ans << endl;
  return 0;
}