#include <algorithm>
#include <cfloat>
#include <climits>
#include <cmath>
#include <complex>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <functional>
#include <iostream>
#include <map>
#include <memory>
#include <queue>
#include <set>
#include <sstream>
#include <stack>
#include <string>
#include <utility>
#include <vector>
 
using namespace std;
 
#define sz size()
#define pb push_back
#define mp make_pair
#define fi first
#define se second
#define all(c) (c).begin(), (c).end()
#define rep(i,a,b) for(int i=(a);i<(b);++i)
#define clr(a, b) memset((a), (b) ,sizeof(a))
#define ctos(d) string(1,d)
 
#define MOD 1000000007

int main(){
  int n,m;
  cin>>n>>m;
  vector<int> v;
  rep(i,0,m){
    int a;
    cin>>a;
    v.pb(a);
  }
  int ans = 1000000000;
  rep(i,0,n+1){
    int c1  = 0;
    int c2 = 0;
    int index = 0;
    int mx = 0;
    int mn = 0;
    while(1){
      if(c1==i)break;
      if(index==m)break;
      if(v[index]>=0){
        c1++;
        mx = max(mx,v[index]);
      }
      index++;
    }
    index = m-1;
    while(1){
      if(c2==n-i)break;
      if(index==-1)break;
      if(v[index]<0){
        c2++;
        mn = min(mn,v[index]);
      }
      index--;
    }
    if(c1==i&&c2==n-i){
      ans = min(ans,mx*2-mn);
      ans = min(ans,mx-mn*2);
    }
  }
  cout << ans << endl;
  return 0;
}