#include <bits/stdc++.h>
#define REP(i,n,N) for(int i=(n);i<(int) N;i++)
#define p(s) cout<<(s)<<endl
using namespace std;
const int inf=1e9;

int main(){
	int N,M;
	cin>>N>>M;
	int D[1010];
	REP(i,0,M){
		cin>>D[i];
	}
        sort(D,D+M);
	int ans=inf;
	REP(i,0,M-N+1){
		int tmp;
		if(D[i]*D[i+N-1]<0){
			tmp=min(abs(D[i])*2+abs(D[i+N-1]),abs(D[i])+2*abs(D[i+N-1]));
		}else{
			tmp=max(abs(D[i]),abs(D[i+N-1]));
		}
		ans=min(ans,tmp);
	}
	p(ans);
	return 0;
}