#include <iostream>
#include <algorithm>
#include <cmath>
#include <vector>
#include <complex>
#include <queue>
#include <deque>
#include <set>
#include <map>
#include <unordered_set>
#include <unordered_map>
#include <iomanip>
#include <assert.h>
#include <array>
#include <cstdio>
#include <cstring>
#include <random>
#include <functional>
#include <numeric>
#include <bitset>
#include <fstream>

using namespace std;

struct before_main{before_main(){cin.tie(0); ios::sync_with_stdio(false);}} before_main;

#define REP(i,a,b) for(int i=a;i<(int)b;i++)
#define rep(i,n) REP(i,0,n)
#define all(c) (c).begin(), (c).end()
#define zero(a) memset(a, 0, sizeof a)
#define minus(a) memset(a, -1, sizeof a)
template<class T1, class T2> inline bool minimize(T1 &a, T2 b) { return b < a && (a = b, 1); }
template<class T1, class T2> inline bool maximize(T1 &a, T2 b) { return a < b && (a = b, 1); }

typedef long long ll;

int main() {

  int N, M; cin >> N >> M;
  vector<int> D(M);
  rep(i, M) cin >> D[i];

  sort(all(D));

  ll ans = 1e10;
  /*
  int zr = upper_bound(all(D), 0) - D.begin(); zr --;
  if(zr >= N-1) {
    minimize(ans, abs(D[zr]) + abs(D[zr] - D[zr - N + 1]));
  }

  if(D[zr] < 0) zr ++;
  if(zr + N - 1 < M) {
    minimize(ans, abs(D[zr]) + abs(D[zr] - D[zr + N - 1]));
  }
  */
  rep(i, M) REP(j, i, M) {
    if(D[i] >= 0 && j - i + 1 == N) {
      minimize(ans, D[j]);
    }
    if(D[j] <= 0 && j - i + 1 == N) {
      minimize(ans, abs(D[i]));
    }
    if(D[i] < 0 && D[j] > 0 && j - i + 1 == N) {
      minimize(ans, abs(D[i]) + abs(D[i] - D[j]));
      minimize(ans, abs(D[j]) + abs(D[i] - D[j]));
    }
  }

  cout << ans << endl;
    
  return 0;
}