#include<bits/stdc++.h>

using namespace std;

int main(){
    int i,j,k,l;
    int m,n;
    int h,x,y;
    
    cin>>n>>m;
    
    vector<int> v;
    
    l=0;
    for (i=0;i<m;i++){
        cin>>j;
        v.push_back(j);
    }
    sort(v.begin(),v.end());
    
    
    int min=-1;
    for (i=0;i<m-n+1;i++){
        l=v[i];
        h=v[i+n-1];
        if (0<=l){
            k=h;
        }else if(0<h){
            int t,u;
            t=(abs(l)*2+h);
            u=(abs(l)+h*2);
            k=t>u?u:t;
        }else {
            k=abs(l);
        }
        //cout<<k<<endl;
        if (min<0||k<min) min=k;
    }
    cout<<min<<endl;
    return 0;
}