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

int main()
{
  int N, M;
  cin >> N >> M;
  vector< int > D(M);
  for(int i = 0; i < M; i++) {
    cin >> D[i];
  }
  sort(D.begin(), D.end());
  int ret = 1e9;
  
  for(int i = 0; i <= M - N; i++) {
    ret = min(ret, max(0, D[i + N - 1]) * 2 - min(0, D[i]));
    ret = min(ret, max(0, D[i + N - 1]) - min(0, D[i]) * 2);
  }
  cout << ret << endl;
}