#include <bits/stdc++.h>
using namespace std;
 
using ll = long long; using ld = long double; using ull = unsigned long long; using uint = unsigned int;
using vi  = vector<int>; using vb  = vector<bool>; using vd  = vector<double>; using vl  = vector<ll>;
using vvi = vector<vi>;  using vvb = vector<vb>;   using vvd = vector<vd>;     using vvl = vector<vl>;
 
#define REP(i,n) for(ll i=0; i<(n); ++i)
#define FOR(i,b,n) for(ll i=(b); i<(n); ++i)
#define ALL(v) (v).begin(), (v).end()

int main() {
	cin.tie(0);
	ios_base::sync_with_stdio(false);
	cout << fixed << setprecision(30);
	ll n, m; cin >> n >> m;
	vl d(m); REP(i, m) cin >> d[i];
	vl fu; REP(i, m) if (d[i] < 0) fu.push_back(d[i]);
	vl sei; REP(i, m) if (d[i] > 0) sei.push_back(d[i]);
	REP(i, m) if (d[i] == 0) n--;
	sort(ALL(sei));
	sort(ALL(fu)); reverse(ALL(fu));

	if (n <= 0) {
		cout << 0 << endl;
		return 0;
	}
	if (fu.empty()) {
		cout << sei[n - 1] << endl;
		return 0;
	}
	if (sei.empty()) {
		cout << fu[n - 1] << endl;
		return 0;
	}

	ll mi = 100000;
	if(n-1 < sei.size()) mi = min(mi, sei[n - 1]);
	if(n-1 < fu.size()) mi = min(mi, -fu[n - 1]);
	REP(i, fu.size()) REP(j, sei.size()) if(i+j+2 >= n){
		mi = min(mi, min(-fu[i] * 2 + sei[j], -fu[i] + sei[j] * 2));
	}

	cout << mi << endl;

	return 0;
}