#include <bits/stdc++.h>
using namespace std;
#define repl(i,a,b) for(int i=(int)(a);i<(int)(b);i++)
#define rep(i,n) repl(i,0,n)
#define mp(a,b) make_pair((a),(b))
#define pb(a) push_back((a))
#define all(x) (x).begin(),(x).end()
#define uniq(x) sort(all(x)),(x).erase(unique(all(x)),end(x))
#define fi first
#define se second
#define dbg(x) cout<<#x" = "<<((x))<<endl
template<class T,class U> ostream& operator<<(ostream& o, const pair<T,U> &p){o<<"("<<p.fi<<","<<p.se<<")";return o;}
template<class T> ostream& operator<<(ostream& o, const vector<T> &v){o<<"[";for(T t:v){o<<t<<",";}o<<"]";return o;}

#define INF 2147483600

int main(){
  int n,m;
  cin>>m>>n;
  vector<int> vec(n);
  rep(i,n) cin>>vec[i];

  sort(all(vec));

  int ans = INF;
  rep(i,n-m+1){
    int tmp = 0;
    int j = i+m-1;
    int u = abs(vec[i]), v = abs(vec[j]);
    if(vec[i]*vec[j]>=0){
      tmp = max(u, v);
    } else {
      tmp = min(u,v) + abs(vec[i] - vec[j]);
    }
//    dbg(tmp);
    ans = min(ans, tmp);
  }

  cout << ans << endl;

  return 0;
}