#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<cmath>
//#include<cctype>
#include<climits>
#include<iostream>
#include<string>
#include<vector>
#include<map>
//#include<list>
#include<queue>
#include<deque>
#include<algorithm>
//#include<numeric>
#include<utility>
#include<complex>
//#include<memory>
#include<functional>
#include<cassert>
#include<set>
#include<stack>
#include<random>

const int dx[] = {1, 0, -1, 0};
const int dy[] = {0, 1, 0, -1};
using namespace std;
typedef long long ll;
typedef unsigned long long ull;
typedef vector<int> vi;
typedef vector<ll> vll;
typedef pair<int, int> pii;

int main() {
    cin.tie(0);
    ios::sync_with_stdio(false);
    int N, M;
    cin >> N >> M;
    vector<int> minus, plus;
    for (int i = 0; i < M; i++) {
        int d;
        cin >> d;
        if (d < 0) minus.push_back(-d);
        else if (d > 0) plus.push_back(d);
        else N--;
    }
    sort(minus.begin(), minus.end());
    sort(plus.begin(), plus.end());
    ll ans = 1ll<<60;
    for (int k = 0; k <= N; k++) {
        if (minus.size() < k) continue;
        int kp = N-k;
        if (plus.size() < kp) continue;
        ll a = 0, b = 0;
        if (k > 0) a = minus[k-1];
        if (kp > 0) b = plus[kp-1];
        ll tmp = a+b + min(a, b);
        ans = min(ans, tmp);
    }
    cout << ans << endl;
    return 0;
}