#include <bits/stdc++.h>
using namespace std;
// #define int long long
using ll=long long;
using vi=vector<int>;
using vl=vector<long long>;
using pii=pair<int,int>;
using pll=pair<ll,ll>;
#define ITR(v,c) for(auto v=begin(c);v!=end(c);v++)
#define FORE(x,c) for(auto &x:c)
#define FOR(v,a,n) for(int v=a;v<(int)(n);v++)
#define REP(v,n) FOR(v,0,n)
#define RREP(v,n) for(int v=((int)(n)-1);v>=0;v--)
#define ALL(c) begin(c),end(c)
#define RALL(c) rbegin(c),rend(c)
#define SZ(c) ((int)c.size())
const int DX[9]={0,1,0,-1,1,1,-1,-1,0}, DY[9]={-1,0,1,0,-1,1,1,-1,0};
const int INF=1e9; const long long INFLL=1e18;
template<class T> ostream& operator << (ostream &os, const vector<T> &v) {
    ITR(i,v) os<<*i<<(i==end(v)-1?"":" "); return os; }
template<class T> istream& operator >> (istream &is, vector<T> &v) {
    ITR(i,v) is>>*i; return is; }
//------------------------------------------------------------------------------

signed main() {
    int n,m;
    cin>>n>>m;
    vi d(m);
    cin>>d;
    sort(ALL(d));
    int ans=INF;
    REP(i,m-n+1) {
        int ret=0;
        int top=d[i],bot=d[i+n-1];
        if(bot<=0) {
            ret=abs(top);
        }
        else if(0<=top) {
            ret=abs(bot);
        }
        else {
            ret=abs(bot-top)+min(abs(top),abs(bot));
        }
        // dump(top,bot,ret);
        ans=min(ans,ret);
    }
    cout<<ans<<endl;
    return 0;
}