#include <bits/stdc++.h>
using namespace std;
struct INIT{INIT(){ios::sync_with_stdio(false);cin.tie(0);}}init;
int main() {
    int n,m;
    cin >> n >> m;
    vector<int> d(m);
    for(auto& it : d)cin >> it;
    sort(d.begin(),d.end());
    int res=114514;
    for(int i = 0,j= n - 1; j < m; i++,j++){
        res=min(res,min(abs(d[i]),abs(d[j]))+abs(d[i]-d[j]));
    }
    cout<< res << endl;
    return 0;
}