#include<iostream>
#include<algorithm>

using namespace std;

int main(){

	int N,M;
	long long ans=100000008;
	int D;
	int pD[1000],mD[1000];
	int pc,mc;

	cin>>N>>M;
	pc=0,mc=0;
	for(int i=0;i<M;i++){
		cin>>D;
		if(D==0) N--;
		else if(D>0) pD[pc]=D,pc++;
		else mD[mc]=-D,mc++;
	}
	pD[pc]=0;
	mD[mc]=0;

	if(pc!=0) sort(pD,pD+pc+1);
	if(mc!=0) sort(mD,mD+mc+1);

	
	for(int i=max(-mc,-N);i<=min(pc,N);i++){
		long long sum=-1;
		if(i==0) continue;
		else if(i<0&&pc-(N+i)>=0){
			sum=mD[-i-1+1]*2+pD[N+i];
			if(N+i==0) sum/=2;
			//cout<<-i-1+1<<"-"<<N+i<<endl;
		}
		else if(i>0&&mc-(N-i)>=0){
			sum=mD[N-i]+pD[i-1+1]*2;
			if(N-i==0) sum/=2;
			//cout<<N-i<<"+"<<i-1+1<<endl;
		}
		//cout<<i<<","<<sum<<endl;
		if(sum!=-1&&sum<ans) ans=sum;
	}

	cout<<ans<<endl;
}