#include<bits/stdc++.h>
 using namespace std;
#define INF 10000000000
#define REP(i,n) for(int (i)=0;(i)<(int)(n);(i)++)
typedef long long ll;
vector<ll> v,w;
long long s1[100002];
long long s2[100002];
int main(){
    REP(i,100002){
        s1[i]=INF;
    }
    int N,M;
    cin>>N>>M;
    REP(i,M){
        int a;
        cin>>a;
        if(a>=0){
           v.push_back(a);
        }else{
           w.push_back(abs(a));
        }
    }
    sort(v.begin(),v.end());
    sort(w.begin(),w.end());
/*
    s1[0]=0;
    s2[0]=0;
    REP(i,v.size()){
       s1[i+1]=s1[i]+v[i];
    }
    REP(i,w.size()){
       s2[i+1]=s2[i]+w[i];
    }
*/
    long long ans=INF;
    if(v.size()>=N){
       ans=min(ans,v[N-1]);
    }
    if(w.size()>=N){
       ans=min(ans,w[N-1]);
    }
    for(int i=1;i<N;i++){
        if((i>v.size())||(N-i)>w.size())continue;
        long long x=min(v[i-1]+2*w[N-i-1],2*v[i-1]+w[N-i-1]);
        ans=min(ans,x);
    }
    cout<<ans<<endl;

    
}