#include <iostream>
#include <algorithm>
#include <vector>
#define REP(i,n) for(int i = 0; i < (int)(n); ++i)
using namespace std;

int main(){
    int N, M;
    cin >> N >> M;
    vector<int> D;
    int t = 0;
    REP(i,M){
        cin >> t;
        D.push_back(t);
        }
    sort(D.begin(),D.end());
    int ans = 114514;
    REP(i,M-N+1){
        if(D[i]*D[i+N-1]<0){
            ans = min(ans, min(abs(D[i])*2+abs(D[i+N-1]),abs(D[i])+abs(D[i+N-1])*2));}
        else{
            ans = min(ans,abs(max(abs(D[i]),abs(D[i+N-1]))));}
        }
    cout << ans << endl;
    return 0;
}