#include <cmath>
#include <cstdio>
#include <vector>
#include <iostream>
#include <algorithm>
using namespace std;


int main() {
	int n, m;
	cin >> n >> m;
	vector<int> d(m);
	for(int i = 0; i < m; i++){
		cin >> d[i];
	}
	sort(d.begin(), d.end());
    
    int sum = 0;
    int minT = 10000000;

    for(int i = 0; i <= m - n; i++){
    	if(d[i] <= 0 && d[i + n - 1] <= 0){
    		sum = d[i] * -1;
    	}else if(d[i] >= 0 && d[i + n - 1] >= 0){
    		sum = d[i + n - 1];
    	}else{
    		sum = d[i + n - 1] - d[i] + min(d[i] * -1, d[i + n - 1]);
    	}
    	if(sum < minT){
    		minT = sum;
    	}
    }
    
    cout << minT << endl;
    
    return 0;
}