#include <iostream>
#include <vector>
#include <algorithm>
using namespace std;
int main(){
	int n,m;cin>>n>>m;
	int ans = 100000000;
	vector<int> A(m);
	for(int i = 0; m > i; i++){
		cin>>A[i];
	}
	sort(A.begin(),A.end());
	for(int i = 0; m-n >= i; i++){
		int t = A[i+n-1]-A[i];
		if(A[i+n-1] <= 0){
			ans = min(ans,0-A[i]);
		}else if(A[i] >= 0){
			ans = min(ans,A[i+n-1]);
		}else{
			ans = min(ans,min(abs(A[i]),abs(A[i+n-1]))*2+max(abs(A[i]),abs(A[i+n-1])));
		}
	}
	cout << ans << endl;
}