#include <bits/stdc++.h>
using namespace std;

int n,m,a[1100];
int main(){
cin>>n>>m;
for(int i=0;i<m;++i)cin>>a[i];
sort(a,a+m);
int ans=1e9;
for(int i=0;i+n-1<m;++i)ans=min(ans,min(abs(a[i]),abs(a[i+n-1]))+abs(a[i]-a[i+n-1]));
cout<<ans<<endl;
}